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DnD 3.5 - The Unseen Seer Handbook

Disclaimer

I will use the color coding scheme which has become common among Pathfinder build handbooks, which tend to be more consistent than 3.5 handbooks. Because so little of 3.5 is available on the SRD, I will attempt to tag items with a superscript indicating their book of origin. For help identifying sourcebook abbreviations, see my Sourcebook Abbreviations Guide.

  • Red: Bad, useless options, or options which are extremely situational.
  • Orange: OK options, or useful options that only apply in rare circumstances
  • Green: Good options.
  • Blue: Fantastic options, often essential to the function of your character.

It's important to note that I generally omit campaign-setting specific content. I am of the opinion that those options are intended to be limited to campaigns run in those settings, and as such they don't really apply to a generic campaign. Those options also tend to be wildly unbalanced and rarely recieve errata. I also omit the use of "Flaws" since they allow a massive increase in power with essentially no cost to the character.

Introduction

The Arcane Trickster came in the core rulebook, and has long been a tantalizing, but largely unplayable character concept. Enter the Unseen Seer: a comensurate professional, a nearly unparalleled dungeoneer, and a welcome addition to nearly any party. The Unseen Seer meshes the Rogue's fantastic skills with the wizard's fantastic divination capacity, and piles a whole bunch of Sneak Attack on top of it all.

The Unseen Seer generally serves as a Rogue-equivalent, filling crucial roles as a Scout and Striker. Depending on your build choices, you can also fill roles as a Face or a Librarian. Depending on your base class choices, your skillset will swing between spellcasting and rogue stuff. If you take only a single level of Rogue before switching to a spellcasting class, you'll only be one level behind a single-class spellcaster, thereby allowing you to serve as a Wizard-equivalent. If you instead emphaize your non-spellcasting base clase, you'll give up spellcasting ability in favor of considerably improved skills.

Because it's so relevant to the Unseen Seer's primary damage mechanic, I strongly recommend reading my article on The "Volley" Rule and discussing it with your DM. Ignoring the rule means that the Unseen Seer is a super-lethal magical machine gun. Using the rule RAW means that you need to do some trickery to be a machine gun. Using my altered rule means that you're still a high-caliber rifle.

Unseen Seer Class Features

Hit Points: d4 hit die is the worst in the game, so you need to go to considerable lengths to avoid drawing fire..

Base Attack Bonus: 1/2 BAB. Fortunately, you won't be relying on anything silly like weapons.

Saves: Will is the Unseen Seer's only good save, but since it's a prestige class you've had two base classes worh of good saves to qualify, which should give you a good base at the very least.

Proficiencies: None. But you really don't need any.

Skills: 6+ skill points won't quite keep pace with a straight Rogue, but you can do a lot of things magically which Rogues must typically do with mundane skills.

Spellcasting: Full spellcasting advancement. Remember that Wizards will still need to spend money to learn new spells, as prestige class spell advanvement does not provide the usual 2 free spells per level ("You do not, however, gain any other benefit a character of that class would have gained").

Damage Bonus: +4d6 Sneak Attack damage over 10 levels isn't quite as good as the Arcane Trickster, but this is a bit of a trick. Your spells will more than make up for the gap.

Advanced Learning (Ex): This is one of the most important abilities of the Unseen Seer. At first glance this is a cute way to get access to some Cleric divinations as an Arcane Caster, but the ability is so much more potent than that. Here are some spells to consider:

  • Arrow MindSpC: If you have decent Dexterity and a passable bow, Arrow Mind can temporarily turn you into an area control Defender. If you're invisible, you can use Sneak Attack on your attacks of opportunity.
  • Divine InsightSpC: 5+caster level is a huge bonus. It's hard to predict what you should use thise for, but it can easily make up for skill points you lost when taking caster class levels, and it can cover the gap for infrequently used (but still essential) skills like Disable Device and Open Lock which aren't on the Unseen Seer skill list.
  • Find the GapSpC: Helpful if you like to use real weapons, but nearly all Unseen Seers rely on spells.
  • GolemstrikeSpC: Learn this by normal means. It should be on your spell list unless you're playing something weird like a beguiler or a bard.
  • Grave StrikeSpC: Cleric spell, and absolutely crucial if you want to be able to handle undead.
  • Guidance of the AvatarWeb: This spell is questionably usable. The article series from which it originates has a lot of poorly balanced content. As a DM I would disallow this spell, but if your DM allows it than this is likely better than Divine Insight.
  • Healer's VisionCS: +2 to attack and damage with Sneak Attacks is nice, but remember that this is a standard action to cast with a rounds per level duration. Also, 2 damage on each sneak attack is a laughably small amount of damage considering how much you're going to be doing.
  • Hunter's EyePHB2: This is probably the most important offensive option available to the Unseen Seer, and it makes up the difference between the Unseen Seer's Sneak Attack and every other Sneak Attack-using build. It's a swift action, and only lasts one round, so you're going to spend a lot of spell slots on it. Remember that since this is a Divination spell, Divination Spell Power boosts your caster level, and therefore your additional Sneak Attack dice. At high levels consider using Persistant Spell. Going from 1 round duratioin to 24 hour duration is a pretty big improvement.
  • Hunter's MercySpC: If you were better with weapons, this would be really cool. But the Unseen Seer is all about spells and precision damage (which doesn't multiply on a crit).
  • VinestrikeSpC: Learn this by normal means. It should be on your spell list unless you're playing something weird like a beguiler or a bard.

Silent Spell: Nice to have, but not essential. If you take this early, when you get it as a bonus feat you're allowed to select any other feat for which you qualify, which is a great way to get access to more high level feats than you could normally have.

Divination Spell Power (Ex): Losing caster levels with other spell schools is slightly annoying, but Practiced Spellcaster can make up the difference, though part of its effect will be eaten by your non-caster qualifying class(es).

Guarded Mind (Su): I wasn't sure exactly how useful Nondetection was, so I did some digging and rescued this excellent interpretation from the (now defunct) WotC forums:

Clairaudience/clairvoyance is a divination (scrying) spell along with arcane eye and prying eyes. Nondetection thwarts divination (scrying).

Locate object and locate creature are thwarted by nondetection. Discern location specifically indicates that it is not thwarted by nondetection. Only mind blank stops discern location.

Detect spells include any spell with "detect" in the title: detect magic, detect undead, detect thoughts, etc. These spells are thwarted by nondetection.

See invisibility, true strike, moment of prescience, foresight, Rary's telepathic bond, tongues, and true seeing are not detection, location, or scrying divination spells. Nondetection has no ability to thwart these divination spells.

So it won't protect you from things like See Invisibility or Invisibility Purge, but it will protect you from more general detection methods like Detect Magic. This is in no way an official ruling, but it's logical enough that I would use it in my games.

Qualifying Classes

Unseen Seer's prerequisites are fairly gentle. 1st-level spells, including a couple divinations, and 8 ranks in a few skills which you probably want anyway. You could qualify with a single level of an arcane spellcasting class and a pile of Rogue levels, or with a bunch of caster levels and a single Rogue level at level 5 so you have enough skill ranks to get those skills up to 8. You don't even need to use Rogue, technically, since Unseen Seer doesn't require Sneak Attack.

More clever combinations are possible, but for the sake of simplicity the classes below all have every required skill except Spellcraft and/or cast arcane spells including enough divinations to qualify for Unseen Seer. Sense motive has also been ignored because you only need 4 ranks, so you can cross-class it if you need to do so. I'm assuming that you want to get into Unseen Seer as quickly as possible, so I assume that you'll take 5 total class levels. This might be a 1/4 split in either direction, but there's a case to be made for 2/3 splits depending on your choice of classes.

  • BardPHB: The Bard is a great utility class with great skills, but it lacks many offensive options with which to capitalize on Sneak Attack, which can make it a difficult option. Bards still get Ice Darts, which is the most important Unseen Seer spell, so it's possible, but the bard's 2/3 spellcasting means that you're giving up a lot of high-level spell slots which you could use for metamagic or utility options. If you're serving as your party's rogue-equivalent this can be a great way to add more skills to your build, but the only party of the bard which you'll carry forward is the spellcasting and the gap in spellcasting between a bard and a sorcerer will become apparent very quickly.
  • BeguilerPHB2: The Beguiler has the ability to roll straight into Unseen Seer without multiclassing. While this can be great utility option, Beguilers have almost no damaging spells (with the exception of the Whelm spells, which only deal nonlethal damage), making them a poor offensive option.
  • DuskbladePHB2: Dusbklades can't know two divination spells until they hit level 5 and get 2nd-level spells. If you dip a single level into another arcane caster class, Duskblade could be an option. They're an intelligence-based spontaneous caster, and the Armored Mage abilities are tempting. Unfortunately, the Duskblade is really built for melee, so many of its spells are touch range, and its abilities are designed for melee attacks.
  • FactotumDung: The Factotum trades the Rogue's Sneak Attack damage for some interesting skill abilities. Brains over Brawn allows you use Intelligence in place of Dexterity for skills, so you can nearly dump Dexterity (don't totally dump it since you need to make ranged touch attacks), making the Unseen Seer essentially a single-stat character. Unfortunately you won't get much mileage out of Arcane Dilletante in the 1-4 levels you can spare before switching to prestige classes.
  • NinjaCAd: Ninja can be a hard class to make viable, especially since you're multiclassing and won't have enough Ki points to fuel your Ninja abilities. However, since the Unseen Seer relies almost entirely on Sneak Attack via flat-footed enemies, Sudden Strike is as good as Sneak Attack. Ghost Step (Invisible) can also be helpful to save on spell slots at low levels. Unfortunately, you don't get Evasion. Since you'll be investing heavily in being undetectable, Evasion provides you a crucial defense against AOEs which may be the only way to defeat you reliably.
  • RangerPHB: Ranger is a bad class, and its most redeeming qualities don't come in until after you've started taking Unseen Seer levels. Coincidentally (not ironically, go look it up), one of the Unseen Seer's favorite spells (Hunter's Eye) is exclusive to Rangers.
  • RoguePHB: The gold standard of Sneak Attack, the Rogue is a great option. Lots of skills, Trapfinding, and Evasion allow the Unseen Seer to fill the role of the party's skill monkey, and give the Unseen Seer a great base for their Sneak Attack-based damage output.
  • ScoutCAd: A many skills as the Rogue and a similar skill list, but 2nd level gives you Uncanny Dodge instead of Evasion, and Skirmish doesn't scale nearly as fast as Sneak Attack.
  • SorcererPHB: The choice between a Sorcerer and a Wizard is much like the normal choice between the two classes. If you need to fill the role of your party's skill monkey, Wizard is better because you get more mileage out of your intelligence, and you're less MAD. If you don't need to be a skill monkey, Sorcerer can be a great option because most of your offensive spells are low level, allowing you to capitalize on the Sorcerer's larger pool of spell slots. Since Unseen Seers rely primarily on a small subset of spells, the sorcerer's limited list of spells known generally won't be a problem. You also get access to powerful options like Arcane Fusion which can provide powerful ways to outpace the action economy.
  • SpellthiefCAr: The Spellthief has the ability to roll straight into Unseen Seer without multiclassing. The Master Spellthief feat makes the Spellthief an especially viable option. Steal Spell can be very powerful, especially if you have other spellcasters in the party or if you fight a lot of enemy spellcasters. Steal Spell Effect doesn't specify that you can't do it at range, so you can start encounters by machine-gunning enemy spellcasters to steal/suppress their buffs. In any case, I wouldn't go past second level. Steal Energy Resistance isn't great, and you'll get more utility from a level or two of Rogue if you want more than two levels of your non-caster class.
  • WarbladeToB: Assassin Stance may allow you to pass the Sneak Attack requirement, depending on your DM. While this is a fun trick, you give up skills and Trapfinding. Since the Unseen Seer is generally the party's Rogue-equivalent, that can be a huge problem.
  • WarlockCAr: The warlock gets an honorable mention here. They can't qualify for Unseen Seer because they can't cast spells, and they can't make use of Advanced Learning. The Unseen Seer's spellcasting progression could technically advance the Warlock's abilities, but it's not a good idea. Warlocks looking for a similar concept should consider the Spellwarp Sniper instead.
  • WarmageCAr: The Warmage gets an honorable mention like the warlock. Warmages get only one Divination spell (True Strike), so they can't qualify without something weird like Arcane Disciple. The Warmage is tempting because of their great offensive options and their ability to cast spells in armor, but they complete lack utility options, especially crucial options like Invisibility.
  • WizardPHB: The best spell list in the game, and the ability to learn essentially every spell on the list. The dependence on Intelligence also helps with your skill points. The Unearthed Arcana Variant Wizard trades in Scribe Scroll for a fighter bonus feat, which can get you something cool like Improved Initiative or Point-Blank Shot. You won't take enough Wizard levels to get the 5th-level bonus feat.

Abilities

The Unseen seer's abilities more strongly reflect their caster class than their non-caster class. Rogue/Wizards, for example, are all about Intelligence. However, since you're not dependent on spell DC to be effective, you can afford not to dump all of your resources into your spellcasting ability.

Str: Dump.

Dex: A bit of Dexterity is helpful for skills, ranged touch attacks, AC, and saves.

Con: Everyone needs hit points and Fortitude saves, but your best bet is typically avoidance rather than endurance.

Int: For intelligence-based builds, this is your primary stat. For Charisma-based builds, you probably still need a lot of Intelligence for skill points.

Wis: Unseen Seer gets good Will saves, and your spellcaster class likely does too, so you can afford to not invest a lot in Wisdom.

Cha: Charisma-based casters will want a bunch of Charisma, but Intelligence-based builds can dump charisma and make up for it with items where necessary.

Intelligence-based Caster
32 Point Buy 28 Point Buy 22 Point Buy 15 Point Buy Elite Array
  • Str: 8
  • Dex: 16
  • Con: 14
  • Int: 16
  • Wis: 12
  • Cha: 8
  • Str: 8
  • Dex: 14
  • Con: 12
  • Int: 17
  • Wis: 13
  • Cha: 8
  • Str: 8
  • Dex: 14
  • Con: 12
  • Int: 16
  • Wis: 10
  • Cha: 8
  • Str: 8
  • Dex: 12
  • Con: 12
  • Int: 14
  • Wis: 8
  • Cha: 9
  • Str: 8
  • Dex: 14
  • Con: 13
  • Int: 15
  • Wis: 12
  • Cha: 10
Charisma-based Caster
32 Point Buy 28 Point Buy 22 Point Buy 15 Point Buy Elite Array
  • Str: 8
  • Dex: 16
  • Con: 12
  • Int: 14
  • Wis: 8
  • Cha: 16
  • Str: 8
  • Dex: 14
  • Con: 12
  • Int: 14
  • Wis: 8
  • Cha: 16
  • Str: 8
  • Dex: 13
  • Con: 12
  • Int: 12
  • Wis: 8
  • Cha: 16
  • Str: 8
  • Dex: 13
  • Con: 10
  • Int: 12
  • Wis: 8
  • Cha: 14
  • Str: 8
  • Dex: 14
  • Con: 12
  • Int: 13
  • Wis: 10
  • Cha: 15

Races

Size doesn't matter since you're using spells, but given the choice opt for small size. Bonuses to your casting stat are crucial, but bonuses to Dexterity are nice if you can't get one. Intelligence and Charisma bonuses simply don't exist in the core rulebook, so consider non-core races if possible.

Dwarf: Nothing useful for the Unseen Seer.

Elf: Bonus Dexterity is nice, but that's really all that you get.

Gnome: The ability bonuses aren't helpful, and the Gnome's other racial abilities aren't very interesting..

Half-Elf: Awful.

Half-Orc: Penalties to both potential caster stats.

Halfling: Small size and bonus Dexterity are nice.

Human: A bonus feat, extra skill points, and access to Able Learner make Humans a great option for skill monkey builds. Unfortunately, Dragonborn of Bahamut strips both your free feat and your bonus skills, so if you want the Dragonblood subtype you'll need to take the Dragontouched feat.

Non-Core Races

Dragonborn of BahamutRotD: The ability score adjustments and the favored class aren't helpful, but Dragonblood subtype without a feat is great, and Draconic Aspect is amazing. Heart is obviously out since a breath weapon on a spellcaster is pointless, but it's hard to decide between Mind and Wings. Mind eventually grants permanent blindsene, which is amazing, but you can get Blindsight as a 2nd-level spell. Wings grants flight, but it only gives you 30 ft. flight with Average Maneuverability, so Overland Flight or Fly will often be better choices.

Silverbrow HumanDM: The Dragonblood subtype is nice, but the reason you play a human is for the feat and bonus skill points.

SpellscaleRotD: Ideal for a Charisma-based build. +2 Charisma is almost impossible to find, and the Dragonblood subtype opens up fantastic feats like Practical Metamagic and improves Arcane Spellsurge. The rituals also offer a few decently useful options.

Skills

This section only covers skills on the Unseen Seer list. Other Rogue skills are often still crucial for the Unseer Seer, but they are beyond the scope of this guide. Humans will want to take Able Learner to easily continue their skill progression, but others will need to invest cross-class ranks to continue improving crucial skills like Disable Device.

  • Bluff (Cha): Helpful if you're the party's Face.
  • Concentration (Con):
  • Deciper Script (Int): Too situational.
  • Diplomacy (Cha): Essential if you're the party's Face.
  • Disguise (Cha): Cast Disguise Self, Alter Self, or Polymorph.
  • Forgery (Int): Too situational.
  • Gather Information (Cha): Helpful if you're the party's Face.
  • Hide (Dex): A bit is nice for when your spells run low, but you can hopefully cast Invisibility, so this shouldn't be an issue most of the time.
  • Knowledge (All) (Int): Knowledge is crucial in any party, so take any important Knowledge skills which your party can't already cover.
  • Listen (Wis): The least important perception skill, but still very helpful.
  • Move Silently (Dex): You can cast Silence to muffle whatever sound you make, but it's very conspicuous, so even while you're invisible is often best to rely on Move Silently.
  • Search (Int): Always essential when looking for traps and such.
  • Sense Motive (Wis): Helpful if you're the party's Face.
  • Spellcraft (Int): Important for identifying spells, but if your party already has a primary caster you can probably skip it.
  • Spot (Wis): Possibly the most rolled skill in the game. Anyone who has it as a class skiill should take it.

Feats

This section does not cover metamagic feats. For help with metamagic, see my Practical Guide to Metamagic

  • Able LearnerRoD: Able Learner allows you to continue improving your Rogue skills at their normal cost while taking Unseen Seer levels. Remember: if a skill is a class skill for any of your classes, your maximum ranks are calculated as though it was always a class skill (level+3). "Regardless of whether a skill is purchased as a class skill or a cross-class skill, if it is a class skill for any of your classes, your maximum rank equals your total character level + 3.". Unfortunately, this is only available to humans and doppelgangers (and Changelings in Eberron campaigns, according to page 116 of RoD, so your DM might allow Changelings across the board).
  • Arcane MasteryCAr: Ice Darts doesn't allow spell resistance, and if you're facing something with spell resistance you can probably still Ice Dart it to death.
  • Arcane ThesisPHB2: This works well on a lot of spells, but it's especially useful on the handful of spells which you live and die by. The Knowledge (Arcana) requirement can be a bit of a problem unless you're an Intelligence-based build since your skill points will be stretched very thin, so you may need to wait until 9th level to take this.
    • Ice Darts: a good choice at 6th level. The +2 caster level bonus gets you another dart early and offsets the caster level reduction from Unseen Seer, but the real draw is the metamagic cost reduction. Suddenly, Silent Quickened Twin Ice Darts is an 8th-level spell and the most horrifying swift action I've ever seen. Even if you omit Quickened Spell in favor of Arcane Spellsurge, dropping one spell level means that Silent Twin Ice Darts is a 5th-level spell, making it much easier to stretch your spell slots.
    • Hunter's Eye: Gets you most of another Sneak Attack die, removes the level increase of Extend Spell, and makes Persistent Spell less costly (and therefore available two levels ealier).
  • DarkstalkerLoM: Crucial. You are absolutely dependent on invisibility, and being revealed by blindsense or something equally annoying will reduce you to a under-leveled and poorly prepared wizard. This feat makes Improved Invisibility nearly as effective as Superior Invisibility, allowing you replace an 8th-level spell with a 4th-level spell.
  • Knowledge DevotionCC: Normally reserved for melee classes, Knowledge Devotion can be a great due to the Unseen Seer's dependence on rays and touch attacks.
  • Metamagic Spell triggerCM: Imagine you have a fully charged wand of a 2nd-level spell like Hunter's Eye, and you you use this with Persist Spell. 7 charges costs 630gp. Possibly worth it at very high levels, but it's going to get expensive very quickly. Still, that may be well worth the cost compared to an 8th-level spell slot.
  • Piercing EvocationCM: Most of the Unseen Seers' damage output is energy damage, so ignoring 10 points of resistance allows you to keep using your favorite spells with less concern for energy types. Of course, depending on your choice of caster class you also have several damage spells which fall under Conjuration, so they won't be covered.
  • Practical MetamagicRoD: This requires the Dragonblood subtype, but if you have it this can be a wonderful option. Selecting Split Ray makes it much less expensive to use, and since it's one of your biggest sources of damage output it's a great choice. Ocular Spell is also a great option since it's something you'll probably do before every fight.
  • Practised SpellcasterCAr: You're giving up at least 1 caster level for your non-caster prerequisite class, and you're giving up three caster levels for non-divination spells, which means Practiced Spellcaster brings you caster level right back up to your character level.
  • Ranged RecallCM: Tempting, but the feat cost is high, and you're making ranged touch attacks. If you can't hit consistently with a ranged touch attack, you have much bigger problems.
  • Residual MagicCM: Considering how much time an Unseen Seer spends spamming their favorite attack spell (Scorching Ray, etc.), this is exceptionally potent. The Enduring Potency effect is fantastic for extending your limited spell slots, especially since most of the Unseen Seer's favorite spells are only first or second level. A Pearl of Power 1 or 2 costs 1000gp or 4000gp, while an eternal wand of your favorite attack spell costs 820gp or 4420gp, and gets you twice as many uses per day. Since you're going to be spamming your favorite attack spell, consider picking up two or three eternal wands since you're going to go through charges quickly. Lingering Metamagic effect allows you to capitalize on expensive metamagic effects like Twin Spell. It's a bit easier to use for spontaneous casters since you don't need to pre-plan its use, but it's fantastic even if you don't end up needing it.

Metamagic Feats

This section does not fully cover metamagic feats. For general help with metamagic, see my Practical Guide to Metamagic. This section briefly touches on a few crucial metamagic feats to consider, and provides relevant information in addition to the general information in my metamagic guide.

  • Extend SpellPHB (+1): Many of your most important spells are swift action single-round buffs, so extending them can double their mileage, and lets you use your swift action for other things.
  • Heighten SpellPHB (+X): Generally only useful for spontaneous casters. Heighten Spell means that even if you only know a 1st-level spell, your Reserve Feat can pretend that you know a spell of your highest level.
  • Ocular SpellLoM (+2): Because using your Ocular spells is a full round action, it gets around the "Volley" rule. However, it turns the spells into single rays, so spells like Scorching Ray and Ice Darts lose their primary draw, and combining this wil Split Ray likely won't work.
  • Persistent SpellCAr (+6): It's rare for someone besides Divine Metamagic users to use Persistent Spell because the cost is so high, but some of the Unseen Seer's most important spells are only 1st or 2nd level, especially Hunter's Eye and and Cloud of Knives. They are absolutely worth a +6 to their spell level.
  • Quicken SpellPHB (+4): An extra spell per round meand an extra application of Sneak Attack. 1st-level spells like Lesser Orb of Acid work just fine, and have decent damage output. Unfortunately Quickened Scorching Ray is the only spell specifically mentioned by "Volley" rule, so unless your group deliberately ignores it, you can't count on that option. The same likely applies to Ice Darts for all of the same reasons. You also need to weigh the use of Quicken Spell against the importance of swift action spells like Hunter's Eye and Golemstrike until you can afford to persist those spells. Around the same time, you'll need to weigh the usefulness of this feat over Arcane Spellsurge.
  • Reach SpellCD (+2): Possibly useful with multi-touch touch range spells like Chill Touch, but very costly. If you really want this, take a level of Archmage for Arcane Reach.
  • Silent SpellPHB (+1): You get it for free as a bonus feat. You might even consider using it. In conjunction with Improved Invisibility and Invisible Spell, no one will ever know you're there.
  • Split RayCAr (+2): Twin Spell for rays at half the cost. Depending on your interpetation of the "Volley" rule, Split Ray is either a huge boost to your damage output or wholly worthless. RAW this won't help except when used to cast a spell as a full round action (spontaneous casters using metamagic, or an Ocular spell will work), but as I explain in my article on the "Volley" Rule, the rule has some issues that may justify ignoring it outright. If your ignore the volley rule, the best uses of this feat are on high-level ray spells like Disintegrate and Enervation which are threatening on their own without relying on Sneak Attack.
  • Twin SpellCAr (+4): Twin Spell Ice Darts is your best offensive option without question. You get to apply Sneak Attack ten times. At +7d6 Sneak Attack, that's equivalent to Split Ray Disintegrate and doesn't allow a save or spell resistance.

Reserve Feats

Reserve feats are very effective for the Unseen Seer because they stretch your magic considerably, and the feats which allow you to make attacks rolls also allow you to apply Sneak Attack. Ideally, your reserve feat should do somewhere close to 1d6 damage per character level, making it a highly effective fallback.

  • Acid SplatterCM: +1 CL for Acid spells, and a touch attack, allowing you to apply Sneak Attack.
  • Aquatic BreathCM: If your campaign requires you to be underwater enough to justify this, you should probably be an aquatic race.
  • Blade of ForceCM: Unless you really like force spells, you can skip this.
  • Borne AloftCM: Nice for getting over obstacles, but by the time you can get this you should be running Overland Flight.
  • Clap of ThunderCM: Melee touch attacks are a very bad idea.
  • Clutch of EarthCM: There aren't enough damaging Earth damage spells to justify this.
  • Dimensional JauntCM: Awful as a standard action.
  • Dimensional ReachCM: Very situational.
  • Drowning GlanceCM: Allows a save and only lasts 1 round.
  • Face-ChangerCM: Buy a Hat of Disguise.
  • Fiery BurstCM: The AOE is nice for most spellcasters, but Unseen Seers work on touch attacks.
  • Hurricane BreathCM: Bull rush is very situational.
  • Invisible NeedleCM: Great for fighting incorporeal enemies, and since its force damage nothing is resitant to it, allowing you to reliably apply Sneak Attack.
  • Magic DisruptionCM: The effect is very minor, and it uses your immediate action.
  • Magic SensitiveCM: You can make Detect Magic permanent for very little gold.
  • Minor ShapeshiftCM: Temporary hit points as a swift action as often as you like. Helpful since you're stuck in 30 foot range, but if you're invisible you're hopefully not taking a lot of damage.
  • Mystic BacklashCM: Only useful against enemy spellcasters with whom you are already in melee.
  • Shadow VeilCM: Allows a will save, and concealment won't be nearly as good as what you could do with a spell.
  • Sickening GraspCM: Melee touch.
  • Storm BoltCM: AOE, no touch attack.
  • Summon ElementalCM: A disposable is a great scout and can trigger traps. In a pinch is can help allies flank.
  • Sunlight EyesCM: Tempting because Deeper Darkness is so easy to abuse, but Ebon Eyes is a 1st-level spell.
  • Touch of DistractionCM: The effect is puny.
  • Wind-Guided ArrowsCM: You can do much better things with an immediate/swift action.
  • Winter's BlastCM: AOE, no touch attack.

Weapons

You should never need to use a real weapon.

Armor

Armor depends heavily on your choice of base classes. Some will allow you to cast in light or even medium armor, while most will not. Mage Armor is always a reliable, cost-effective option, so don't be afraid to default to Mage Armor. If you want to wear armor crystals (potentially a very good idea), pick up a suit of Thistledown Padded ArmorRoW and/or a mithral buckler.

Spells

Unseen Seer spells can range anywhere from "I'm a wizard who happens to have Sneak Attack" to "I'm a Rogue, but look at this magical machine gun". I can't possibly list every spell that could possibly be useful, but here are a few essentials.

1st-Level Spells

  • Distract AssailantSpC: A great way to gurantee Sneak Attack, but it allows a save, which might be a problem with a 1st-level spell.
  • Ebon EyesSpC: See normally in all darkness conditions, including magical darkness like Deeper Darkness. Only demons can replicate this ability, so magical darkness suddenly becomes like perpetual invisibility for your whole party.
  • Golem/Grave/Vine StrikeSpC: Sneak Attack is the big draw for the Unseen Seer, so you need a way to Sneak Attack monster types which normally can't be affected by precision damage. Fortunately these spells are low level, and are cast as a swift action.
  • Instant LocksmithSpC: Situational, but a nice little boost to your Disable Device and Open Lock checks, and you make the whole check as a swift action instead of spending a minute or whatever it normally takes.
  • Kelgore's Fire BoltPHB2: Until your caster level is high enough that Lesser Orb of X does more damage, this is a fine option. The ability to deal fire damage even if it fails to overcome spell resistance reduces your reliance on acid spells and Energy Substitution.
  • Lesser Orb of Acid/Cold/Electricity/Fire/SoundPHB: Solid damage on a ranged touch attack. The Acid version doesn't allow Spell Resistance, making it a reliable way to Sneak Attack constructs when combined with Golemstrike.
  • Ray of EnfeeblementPHB: Strength damage is damage, so you get to deal bonus negative energy damage with your Sneak Attack.
  • Ray of FlamePHB: Not as much damage as the Orb of X spells, but it sets the target on fire, which can deal a lot of ongoing damage to enemies with poor Reflex saves.
  • Serene VisageSpC: A decent bonus to Bluff, so you can save a few skill ranks.
  • Sniper's ShotSpC: Ignore that 30 foot range limitation on Sneak Attack, and lazer someone to death from several hundred feat away.

2nd-Level Spells

  • Alter SelfPHB: Alter Self is a frequently overlooked but absurdly powerful spell. At some point I'll write a guide for using it, but for the moment do some googling for "Alter Self Forms".
  • Cloud of KnivesPHB2: A great option to start early in a fight. An attack as a free action every round means an extra chance to deal sneack attack damage. The attack uses your caster level plus your casting ability modifier, so be sure to pick up Practiced Spellcaster as you advance in Unseen Seer so that Divination Power doesn't cut into your attack bonus too much. The attack is a normal attack, not a touch attack, so you actually need a decent bonus to reliably hit things. This is a great candidate for Persist Spell, right behind Hunter's Eye.
  • DarkboltBoVD/LoM: Half of the damage is typeless, making this a reliable to deal partial damage if your other energy options aren't doing the trick. You can also stun the target, but Unseen Seers aren't good at spell DCs so don't count on it.
  • GlitterdustPHB: Blind enemies and reveal invisible creatures at the same time.
  • Hunter's EyePHB2: This should almost definitely be your first choice for Advanced Learning since it's not on the Sorcerer/Wizard spell list. The damage boost is especially potent since Unseen Seer boosts your Divination caster level. Until you can persist this, consider using Extend Spell so that it only eats your swift action every other round instead of every round.
  • Ice DartsFB: Unquestionably better than Scorching Ray. You cap out at 5 attacks instead of 3 and Ice Darts doesn't allow spell resistance. Ice Darts won't do as much damage on its own as Scorching Ray, but the difference of 12d4 vs. 12d6 averages to a total of just 12 damage. If you have just 2d6 of sneak attack (I don't even know how you would do that by CL 11), the two extra d6's of damage will close the damage gap. When you bring in high-level options like Split Ray Disintegrate, this may remain your best option. Adding Twin Spell makes this the undisputed best option.
  • InvisibilityPHB: Obviously.
  • KnockPHB: Why waste ranks on Open Lock?
  • Life BoltSpC: For a pittance of hit points, you can fire up to 5 bolts at undead.
  • Ray of StupidityPHB: Intelligence damage is damage, so you get to deal bonus negative energy damage with your Sneak Attack. Plus, at 1d4+1 damage it's guranteed to incapacitate nearly every animal with no save.
  • Scorching RayPHB: Ice Darts is objectively better.
  • Whirling BladeSpC: Your BAB won't be fantastic, but if your enemies are flat-footed (or you're invisible) you might be able to use this to get several Sneak Attacks in a line. However, the "Volley" rule issue probably still applies. Check with your DM.
  • Wracking TouchSC: Guranteed Sneak Attack damage, but the target gets to save for half and you only get one application of Sneak Attack. Save the spell slot.

3rd-Level Spells

  • FlyPHB: Flight is fantastic, but at some point you'll upgrade to Overland Flight.
  • IcelanceSpC: Single-target attack with fixed damage, but it also has the ability to stun the target.
  • Melf's Unicorn ArrowPHB2: The attacks don't match Ice Darts until caster level 17, and the damage isn't much better than Ice Darts, but you get to bull rush enemies.
  • Stars of ArvandorBoED: Similar to Cloud of Knives, Stars of Arvandor gives you another attack as a free action. However, Stars of Avandor has some key advantages: the attacks are ranged touch attacks instead of regular attacks, and since it's a force effect you don't need to worry about DR and you can attack ghosts. However, you never get more than 10 shots so you can't use Persistent Spell to make this last all day.

4th-Level Spells

  • Black TentaclesPHB: Grappling a creature makes them flat-footed, which means that you can Sneak Attack them.
  • Dimension DoorPHB: Great for getting out of grapples, but not always important.
  • HailstonesSC: Once you hit caster level 20 this will do more damage than Scorching Ray, but it will never do more damage than Ice Darts.
  • Invisibility, GreaterPHB: This is one of the most important spells available to you. Every fight should start with you invisible, and should end before you become visible again.
  • Orb of AcidSpC: If you want a spell that won't allow Spell Resistance, Lesser Orb of Acid will suffice.
  • Orb of ColdSpC: Blinding a target makes them viable for Sneak Attack, but the duration is only 1 round so you will only benefit with quickened spells.
  • Orb of ForceSpC: Great for incorporeal enemies, and solid damage that can't be resisted.
  • PolymorphPHB: Polymorph is insane, and if you have it and don't take it you're making a mistake.
  • Ray of DeanimationPHB: Decent damage to constructs, but you can easily outpace this by combining Golemstrike with other spells that don't allow Spell Resistance (like Ice Darts) since multiple applications of Sneak Attack can so easily outpace caster level-based damage.

5th-Level Spells

  • Arcane FusionCM: Exclusive to Sorcerers, but an absolutely fantastic option. I'm not certain how metamagic works with this, so discuss it with your DM. You might be able to quicken this to cast Split Ray Scorching Ray and an Orb of X all as a swift action, then use the rest of your turn to do other crazy stuff.
  • Lesser Spell MatrixSC: Cast Ice Darts into this and get it quickened. Once you get Arcane Spellsurge or Spell Matrix, this stops being useful.
  • Lord of the SkyDr: Flight and a ranged rouch attack each round that deals lightning damage. With rounds/level duration this can get you through multiple fights if you're quick.
  • Overland FlightPHB: Only average maneuverability, but its hard to argue with hours/level duration.

6th-Level Spells

  • Imbue Familiar With Spell AbilityCAr/SC: Share Spells means the Hunter's Eye works on your familiar. Give your familiar some low-level spells and turn it into a weapon.

7th-Level Spells

  • Arcane SpellsurgeDM: This spell really changes the way spellcasting works. You can't selecticely use the effect, so the best way to use it is for spontaneous casters to use it to cast normal spells as swift actions and metamagic spells a standard actions. If you can handle this weird limitation, it's free quickening on as many spells as you can cast in a rounds/level duration. This can be a great option if you want to cast it then follow it up with Improved Invisibility as a swift action. If you have the Dragonblood subtype (Spellscale is a great optio for Charisma-based build), casting this as a swift action means that you can cast a Full-round action spell (such as a spell affected by metamagic) as a Standard Action. That balances the action cost between Spellscale Sorcerer-based build and Wizard-based builds, but doesn't improve the spell betond that.
  • DisintegratePHB: It allows a fortitude save, but if your DC is decent and you target things with poor fortitude saves (undead, other casters, etc.) the damage is absolutely ridiculous. Split Ray makes it especially horrifying.
  • Spell MatrixSC: Cast Ice Darts into this twice, and you can cast both with the same swift action (see the bit about a "spell sequence" in the spell's text). Arcane Spellsurge will help you more in long fights, but Spell Matrix will let you prevent fights from becoming long.

8th-Level Spells

  • Greater InvisibilitySpC: Rarely a significant improvement on Improved Invisibility, especially with the addition of the Darkstalker feat.
  • Polar RayPHB: Not very exciting, but it's solid damage on its own.

9th-Level Spells

  • Greater, Spell MatrixSC: The "greater" version loses the "spell sequence" mechanic which makes the standard version so good for the Unseen Seer, but it adds a contingency spell option which you can use for things like buffs without cutting into your damage output.
  • Meteor SwarmPHB: 4 attacks with a pile of bludgeoning damage and nice AOEs. Split Ray Scorcing Ray will do comparable damage, but this doesn't require metamagic.

Magic Items

Rings

  • DarkhiddenMIC: One of the best items for sneaky characters. It's startlingly cheap, and if you party all has darkvision this is essentially perpetual improved invisibility.
  • EvasionDMG: If you're not a Rogue you probably won't have Evasion, so this can be a great option. Big AOEs are a very easy way to handle enemies which you can't see, and this takes away a lot of their power.
  • InvisibilityDMG: Always a classic, though very expensive. There's no reason for you to be visible unless you're interacting peacefully with something, so spam this constantly.

Rings

I won't go individual rods, but metamagic rods of metamagic feats like Silent Spell and Invisible Spell are great because those feats aren't always important, but they can be a nice trick once in a while. See my Practical Guide to Metamagic for help with metamagic feats which you might want on a rod.

Wands

  • GolemstrikeSpC: Thanks to the Rules Compendium, activating a wand takes the same casting time as the original spell. Also see Golemstrike under Spells, above.
  • GravestrikeSpC: See Gravestrike immediately above, and the spell analysis under Spells, above.
  • VinestrikeSpC: See Vinestrike immediately above, and the spell analysis under Spells, above.

Wondrous Items

Unseen seer items look a lot like items for Wizards and items for Rogues, so check out my Rogue Handbook and Wizard Handbook. You'll find items that enhance your caster level extremely useful since they boost your Sneak Attack damage from Hunter's Eye, and you may consider a metamagic rod for quicken spell so that you don't need to cast Arcane Spellsurge when you know you can end a fight in one turn.

Permanent Spells

  • Reduce PersonPHB: Since you're not using a weapon being small or tiny is very beneficial. You're much harder to spot, and the size bonus to AC and attacks are always welcome. Just be sure to have a way to escape grapples.

Other Classes

  • ArchmageDMG: Arcane Reach and Spell Power are both useful options, buit aren't essential.
  • Arcane TricksterDMG: Not an awful choice when you run out of Unseen Seer levels, but Spellwarp Sniper offers quite a bit more offensively. The Arcane Trickster's only advantage over the Spellwarp Sniper is the skill list, and getting into Arcane Trickster requires 7 ranks in Disable Device and Escape Artists, which aren't on the Unseen Seer class list. You'll probably want to get most of the ranks between levels 1 and 5 where your skill ranks are already stretched very thin.
  • Master SpecialistCM: You likely won't get enough levels in Master Specialist to get anything interesting. That said, the prerequisites and the free Skill Focus (Spellcraft) line up nicely for Archmage.
  • Spellwarp SniperCS: Several great abilities. Sudden Raystrike is essentially Sneak Attack, and the Ray Mastery ability extends your Sneak Attack range to a nice, safe 60 feet. You may be able to use Spellwarp to turn Ice Darts into days so that you can use Split Ray, but that's a bit of a stretch since Ice Darts doesn't have an "area" to transform.

Example Build - Spellscale Spellthief Sor-seer-er

Sssssssneak attack!

I generally build for what will be the most mathematically effective based on easily assessed criteria, leaning heavily toward things which are known to work very well. This build is a bit of a departure from that philosophy; I don't like the Spellthief class, and I pick Wizard over Sorcerer essentially every time. I'm also extremely hesitant to use metamagic since on a Wizard there's almost always a better spell that can replace a metamagic spell. So, naturally, I combined the three.

This is a weird build. It's is as much an experiment as it is a suggestion, and as I write this paragraph I honestly have no idea how well this will turn out. However, assuming that we hit the most crucial points of the Unseen Seer (Ice Darts, Hunter's Eye, Twin Spell) it's hard for the build to fail so badly that it's not insanely lethal.

At 20th level, this will be a Rogue 1/Sorcerer 2/Spellthief 2/Unseen Seer 10/Arcane Trickster 5. Spellwarp Sniper works in place of Arcane Trickster, but I want Arcan Trickster for the skill list since Unseen Seer loses much of the Rogue's skill list, especially crucial options like Disable Device and Open Lock. I still see the Unseen Seer as more of a rogue-equivalent than a wizard-equivalent, so we need to fill the classic Rogue roles. You can probably replace the rogue level with another Sorcerer level, but you'll give up basically every skill that you don't need to qualify for a prestige class until you hit Unseen Seer.

Restrospective: Oh, god, I've created a monster. The build is really difficult until level 10, at which point it starts ramping up in damage and effectiveness at a truly startling rate. It outperforms Disintegrate by level 12 using a single 2nd-level spell slot, and tripples Disintegrate damage with that same spell slot by level 17. With Twin spell, you can easily kill entire encounters in a single turn at most levels above 10. You can also steal spells and spell effects from anything unfortunate to be within 30 feet of you.

Abilities

We will assume the 32-point buy abilities suggested above for Charisma-based spellcasters, but we'll swap Dexterity and Intelligence. That means that we're starting with 16 Intelligence and 16 Charisma, but like I said: this is a weird build. If you replaced the rogue level mentioned above with an extra Sorcerer level you'll either need to play a human for the skill ranks or make the same ability adjustment.

Race

Spellscale. The Charisma bonus is nice, and we get the dragonblood subtype. You can use some of the blood-quickening rituals to get access to some useful stuff, too. Human with the Dragontouched feat would work equally well, and the extra skill points would be helpful.

Skills

Skills get a bit messy here since the shifting classes have such different class skill lists.

Levels

Level Feat(s) and Features Notes and Tactics
1 - Rogue 1
  • Feat: Darkstalker
  • Sneak Attack +1
  • Trapfinding (ACF?)

At this level you're a weak rogue. Darkstalker won't pay off until much higher level, and with just 14 Dexterity you're not much of a threat.

2 - Sorcerer 1
  • Summon Familiar (ACF?)

With only one die of sneak attack damage, you're not going to scare anyone. Use Acid Splash to deal Sneak Attack, and save your 1st-level slots for a save-or-suck spell like Color Spray or Sleep.

Since we're only taking 2 levels of Sorcerer, your familiar is going to be pretty weak. It won't even be able to deliver touch spells. However, several familiars provide options that will fill in gaps in the build. All of the clases in the build have poor Fortitude saves, and having your familiar handy grants the effects of the Alertness feat, allowing you to slack a bit on your Spot/Listen skill ranks. Personally I recommend the rat for the +2 fortitude save bonus since you'll only get +5 base Fortitude by 20th level.

3 - Sorcerer 2
  • Feat: Extend Spell

Extend Spell won't be helpful yet, but it's an investment in your future. Continue being a terrible sorcerer for now.

4 - Spellthief 1
  • Ability Increase: Charisma
  • Sneak attack +1d6
  • Trapfinding
  • Steal Spell (0- of 1st-level)

A second d6 of Sneak Attack helps a little bit, but your best offensive options are Acid Splash and Kelgore's Fire Bolt, neither of which are especially powerful.

See if your DM will allow you to trade Trapfinding for a Rogue ACF which replaces Trapfinding. Literally anything is better then getting Trapfinding a second time.

5 - Spellthief 2
  • Detect magic
  • Spellgrace +1
  • Steal spell effect

Taking the second level of Spellthief this late allows you to easily reach the required 8 Hide, Search, and Spot ranks without spending twice as many skill points to get them as cross-class skills. Steal Spell Effect is excellent, and the text doesn't have a spell level limit like Steal Spell does, so even if you never take Master Spellthief you will always be able to steal enemies' buffs when you hit them..

6 - Unseen Seer 1
  • Feat: Twin Spell
  • Damage bonus +1d6
  • Caster Level 3

From here on I'll list your normal caster level and your Divination caster level. It gets complicated.

Advancing your caster level and the first Unseen Seer Damage Bonus means that your firebolt is doing 3d6+3d6 on a Sneak Attack.

Your first level of Unseen Seer also means that, for the first time, your skills aren't a complete nightmare. You'll want to put 7 ranks into Decipher Script, but you'be got a while to do that so don't worry about it too much.

7 - Unseen Seer 2
  • Advanced learning (Divine Insight)
  • Bonus Feat: Silent Spell
  • Caster Level 4

This level brings 2nd-level spellcasting. It's really hard to wait until level 7 to get 2nd-level spells as a Sorcerer, but I promise it'll all be worth it soon.

You only get 1 regular spell known, so it's hard to know device what to learn. Invisibility is probably your best bet, but if you're getting by on mundane hiding (or if you have a Ring of Invisibility) go for Cloud of Knives or Ice Darts.

Your first Advanced Learning spell should be Divine Insight. At Caster Level 4, Hunter's Eye only gets you +1d6 Sneak Attack currently so it's not a significant damage boost. Divine Insight will help fill in the huge gap in your rogue skills, especially Disable Device. Relying on Divine Insight also means that instead of investing skill ranks in a bunch of skills which you can't always use, you can put ranks into frequently used skills like Spot and fill in the gaps with magic.

8 - Unseen Seer 3
  • Ability Increase: Charisma
  • Divination spell power +1
  • Caster Level 4 (6 Div)

Mostly a dead level.

9 - Unseen Seer 4
  • Feat: Master Spellthief
  • Damage bonus +2d6
  • Caster Level 7 (9 Div)

Master Spellthief is a big help. Adding 2 caster levels on top of your normal advancement does a lot for your damage output, bringing you up to 3 darts from Ice Darts, and improving your damage from Lesser Orb of X spells enough that you should replace Khelgore's Fire Bolt if you haven't done so already. You could reasonably take Practiced Spellcaster in place of Master Spellthief, but the appeal of Spellthief is stealing spells. If you want Practiced Spellcaster, use Rogue instead of Spellthief.

At this level, Ice Darts will fire three darts, dealing 2d4+4d6 damage each on a Sneak Attack.

3rd-level spells means that you've got enough spell slots to get through a few fights using Ice Darts and other spells. With Extend Spell you can make Hunter's Eye last two rounds, allowing you to spend your 2nd-level spell slots on Ice Darts. You can also now steal spells up to 3rd level, finally making your Spellthief levels somewhat worthwhile.

10 - Unseen Seer 5
  • Advanced learning (Hunter's Eye)
  • Guarded mind
  • Caster Level 8 (10 Div)

This is where the build really starts to take off: you finally pick up Hunter's Eye. At caster level 10 with Divination spells, Hunter's Eye gives you +3d6 Sneak Attack per attack.

You're still getting three darts from Ice Darts, but now you're dealing 2d4+7d6 per dart. Against a single target, that's 6d4+21d6 damage. You're quickly approaching Disintegrate-scale damage, and your damage output will scale very quickly from here on.

11 - Unseen Seer 6
  • Divination spell power +2
  • Caster Level 8 (12 Div)

This level brings 4th-level spells, and Hunter's Eye adds another d6 of damage.

You're still getting three darts from Ice Darts, but they're now dealing 2d4+8d6 per dart. Against a single target, that's 6d4+24d6 damage.

12 - Unseen Seer 7
  • Ability Increase: Charisma
  • Feat: Arcane Thesis (Hunter's Eye)
  • Damage bonus +3d6
  • Caster Level 9 (13 Div, 15 H.E.)

All of the damage ever! You get another Unseen Seer Damage Bonus and Ice Darts finally adds a fourth dart.

Arcane Thesis (Hunter's Eye) now means that you can cast Hunter's Eye both extended and silenced without increasing its spell level. If you'd like, you can cast Silent Ice Darts as a 3rd-level spell, and be completely silent when killing stuff. Arcane Thesis also grants a +2 caster level increase with the specified spell, so your effective caster level with Hunter's Eye hits 15 and brings in yet another damage increase!

You're now getting four darts from Ice Darts, dealing 2d4+10d6 per dart. Against a single target, that's 8d4+40d6 damage. That's more damage than disintegrate cast by a 20th-level spellcaster, and you're using a 2nd-level spell.

13 - Unseen Seer 8
  • Advanced learning (Grave Strike)
  • Caster Level 10 (14 Div, 16 H.E.)

This level brings 5th-level spells, which include a couple really great options addressed under "Spells", above.

14 - Unseen Seer 9
  • Divination spell power +3
  • Caster Level 10 (16 Div, 18 H.E.)

I'm really enjoying the cadence of the past several levels. You get either a huge damage boost or a new spell level. Either is a ton of fun, so leveling is really exciting.

This level brings another d6 of Hunter's Eye. It's not as exciting as the past several levels have been, but just wait until you see what you get at level 15.

You're now getting four darts from Ice Darts, dealing 2d4+11d6 per dart. Against a single target, that's 8d4+44d6 damage. That's more damage than disintegrate cast by a 20th-level spellcaster solely based on the Sneak Attack damage.

15 - Unseen Seer 10
  • Feat: Practical Metamagic (Twin Spell)
  • Damage bonus +4d6
  • Caster Level 11 (17 Div, 19 H.E.)

A lot happens at this level. Like, a whole bunch.

First: You get 6th-level spells. That means that you can cast Twin Spell Ice Darts, doubling your damage output with a standard action. 6th-level spells also include Arcane Spellsurge, which means you can cast Arcane Spellsurge as a swift action (thanks Dragonblood subtype!), Improved Invisibility n in the same turn, and still walk around. Next round, Ice Darts and Twinned Ice Darts!

Remember how I mentioned Twinned Spell Ice Darts? Practical Metamagic (Twin Spell) means that you can do it as a 5th-level spell instead of a 6th-level spell. You have at least twice as many 5th-level spell slots as 6th at this level, so that's pretty great. You can also twin other spells, but they're not as important.

Finally, you get the last insane damage spike. You finally hit caster level 11, giving you the final dart from Ice Darts. You also get the final Unseen Seer Damage Bonus.

You're now getting five darts from Ice Darts, dealing 2d4+11d6 per dart. Against a single target, that's 10d4+55d6 damage. Suck it, every evoker in existence. Don't forget that you can use Twin Spell to double that.

16 - Arcane Trickster 1
  • Ability Increase: Charisma
  • Ranged Legerdemain 1/day
  • Caster Level 12 (18 Div, 20 H.E.)

Finally we make it to Arcane Trickster. Your skill list will change a bit, which will be momentarily annoying. Hunter's Eye also increases at this level, so you're getting yet another Sneak Attack die.

17 - Arcane Trickster 2
  • Sneak Attack +1d6
  • Caster Level 13 (19 Div, 21 H.E.)

8th-level spells and a total of two more Sneak Attack dice.

You're now getting five darts from Ice Darts, dealing 2d4+13d6 per dart. Against a single target, that's 10d4+65d6 damage. Suck it, every evoker in existence. Don't forget that you can use Twin Spell to double that.

18 - Arcane Trickster 3
  • Feat: Persistent Spell
  • Impromptu Sneak Attack 1/day
  • Caster Level 13 (20 Div, 22 H.E.)

I normally don't extend build guides this far since I've generally proven the concept of the build well beforehand. However, I wanted to point out Persistent Spell at 18th level.

Thanks to Arcane Thesis, you can use Metamagic feats with Hunter's Eye at reduced cost. Persistent Spell increases spell levels by +6 (+5 thanks to Arcane Thesis), but having your second-favorite spell always active means that that you don't need to spend a swift action every other turn (not to mention all of those spell slots) to keep it running. This means a huge increase in the amount of damage you can deal in a day since your spell slots are less in demand, not to mention the improved action economy.

You can also use Persisten Spell on Cloud of Knives. It's a regular attack so you won't be as effective with it as you are with Ice Darts, but it's potentially another application of Sneak Attack each round, and at 13d6 that's a nice pile of damage. You may also be able to apply it to your familiar, which means your pet rat gets a free attack every round too.