Resting our head

On the seabed

In an octopus’ garden

Near a cave

Octopus’ Garden – The Beatles

Introduction

Tentacles and dark ocean depths are a Fathomless Warlock’s best friend. While it’s certainly far more useful in an aquatic situation, the Fathomless can hold its own on land as well. So if you don’t shy away from that which wriggles around in mucosal secretions, grab hold of my tentacle and take the plunge. We promise you’re not allowed to drown. Not anymore.

Silly intro aside, the Fathomless Warlock has a pseudopod pseudo-pet, the Tentacle of the Deeps, that can smack things and protect allies. Alongside that, Fathomless has a decent spell list with some fun options, including Black Tentacles. We’ll discuss these features and more in full below.

Our example build, Never Safe From Water, does some fun tricks by creating various zones of safety as well as harm, thanks to features like the Tentacle of the Deeps and Black Tentacles. By utilizing the Pact of the Talisman and its invocations, we, or our chosen partner, are never caught out in a sticky situation. Adventuring is a dangerous business after all; always wear protection.

Table of Contents

Disclaimer

RPGBOT uses the color coding scheme which has become common among Pathfinder build handbooks, which is simple to understand and easy to read at a glance.

  • Red: Bad, useless options, or options which are extremely situational. Nearly never useful.
  • Orange: OK options, or useful options that only apply in rare circumstances. Useful sometimes.
  • Green: Good options. Useful often.
  • Blue: Fantastic options, often essential to the function of your character. Useful very frequently.

We will not include 3rd-party content, including content from DMs Guild, in handbooks for official content because we can’t assume that your game will allow 3rd-party content or homebrew. We also won’t cover Unearthed Arcana content because it’s not finalized, and we can’t guarantee that it will be available to you in your games.

The advice offered below is based on the current State of the Character Optimization Meta as of when the article was last updated. Keep in mind that the state of the meta periodically changes as new source materials are released and this article will be updating accordingly as time allows.

RPGBOT is unofficial Fan Content permitted under the Fan Content Policy. Not approved/endorsed by Wizards. Portions of the materials used are property of Wizards of the Coast. ©Wizards of the Coast LLC.

Fathomless Features

  1. Expanded Spell List: A lot of situational options, and the combat options aren’t great. The spell list gets a little better if you’re underwater frequently, but even then there’s not a lot to be excited about.
    • 1st-level Spells: Two situational options. Thunderwave is fine if you get stuck in melee or need to break a grapple, but I wouldn’t consider it a go-to damage option because getting close enough to hit multiple targets often means getting into melee by choice.
    • 2nd-level Spells: Gust of Wind is very situational, but Silence is a huge problem for enemy spellcasters, especially if your party can keep them inside the area by grappling them, hitting them with a tentacle which applies a speed reduction, or otherwise inhibiting their movement.
    • 3rd-level Spells: Lightning Bolt is fine damage, but hitting more than two targets with line effects is hard regardless of the line’s length. Sleet Storm is decent area control but very hard to use effectively, doesn’t scale with spell slot level, and requires Concentration.
    • 4th-level Spells: Control Water is very situational in non-aquatic campaigns, and limiting Summon Elemental to water elementals similarly handicaps the spell unless you’re in an aquatic campaign.
    • 5th-level Spells: Bigby’s Hand is a great, versatile spell. Cone of Cold is decent if unremarkable AOE damage, but if you need area damage you’ll have better results with Hunger of Hadar.
  2. Tentacle of the Deeps: At 1st level, this matches the effects of Ray of Frost (at least in terms of damage and the secondary effect. With a 1-minute duration it will get you through a single encounter each time you use it, provided that the encounter doesn’t move too far away from the tentacle to reasonably bring the tentacle back into range. This reduces your reliance on Hex at low levels, allowing you to use your one or two spell slots elsewhere without sacrificing damage output. However, since the daily usage limit is tied to your Proficiency Bonus, you won’t be able to use this as often as you could use Hex. Consider the two options complements to each other: use Hex if you just need to Eldritch Blast stuff, and use Tentacle of the Deeps when you need to use Concentration on something other than Hex.
  3. Gift of the Sea: Great in an aquatic campaign, but otherwise very situational.
  4. Oceanic Soul: Damage resistance is great, and, in an aquatic campaign, the ability to speak to all submerged creatures will make it much easier for you to play a face. However, outside of aquatic campaigns you may find it difficult to convince creatures to talk to you while underwater unless you already share a language.
  5. Guardian Coil: You likely don’t have any interesting ways to use your Reaction, so using it to reduce damage to yourself or an ally is an excellent addition to your capabilities. With a 1-minute duration on your tentacle, you could reduce up to 10d8 (20d8 at level 10) damage every time you use it, dramatically improving your party’s ability to handle damage without resorting to in-combat healing.
  6. Grasping Tentacles: Evard’s Black Tentacles is a good spell. I don’t know if it’s better than Hunger of Hadar, but the added benefits from this feature certainly help. You get to cast this once per day for free, which helps with the Warlock’s tiny pool of spell slots, and any time you cast it (free or otherwise), you get temporary hit points. Being unable to lose Concentration on black tentacles due to taking damage also helps quite a bit in combat, making this an easy go-to option in dangerous situations.
  7. Fathomless Plunge: With a 1-mile range, this isn’t exactly a long-distance teleportation option. Rather, this is a panic button. When things are going poorly, grab your friends and retreat to a nearby body of water. However, keep in mind this feature has very strict limitations. You can bring 5 other willing creatures, so if your party is bigger than that you’re in trouble. There’s also some debate over whether unconscious allies can be “willing”, so if allies are down you might not be able to save them. The 1-mile range is small, so you need to be very careful to stay near a suitable body of water, which is hard when you’re delving dungeons or wandering the planes. Of course, it’s great if you’re in an ocean because you can just pop out in a different part of the ocean.

Fathomless Ability Scores

We like all the same ability scores that other Warlocks like. High Charisma for casting and interpersonal skills, decent Dexterity for AC and flexibility, and Constitution for going all night long.

Str: Of all the scores, this is the most likely to get dumped, as of the scores we don’t need it has the least important Saves.

Dex: We’ll want at least some for AC purposes. While we don’t naturally get Medium armor, if we can multiclass or grab Moderately Armored then a 14 is good enough.

Con: This is for HP, Concentration, and saves that suck.

Int: Of the dumpable stats, we can put leftover points here since Arcana is a useful skill for any caster.

Wis: These saves suck to fail, but we have proficiency, so we can let this go.

Cha: Our casting stat. Really important.

Point BuyStandard Array
Str88
Dex1413
Con1514
Int1012
Wis810
Cha1515

Fathomless Races

As far as races, The Fathomless Warlock doesn’t differ too much from what is covered in the Warlock Race Breakdown, but because we get a swim speed and water breathing, it would be redundant to choose a race with those features. So just avoid that and you’ll do fine.

Fathomless Feats

The Fathomless doesn’t need anything different from other Warlocks, so instead I’ll discuss the feats I use in the example build below.

  • Moderately ArmoredPHB: If you can multiclass, it’s usually better to just grab a level of Fighter, but we try to avoid multiclassing in our examples. Medium Armor and a shield is honestly pretty good, especially for casters, who can carry a component pouch so they have a free hand opposite the shield. This is mostly thanks to 5E’s bounded accuracy, which makes AC worth investing in and Medium Armor happens to be the easiest to invest in as far as ability scores go.
  • Resilient (Constitution)PHB: In any of my guides, you’ve probably heard me go on about this feat at length. It really is such a good option, not only improving Concentration saves but also protecting against many dangerous save-or-suck effects. Funny though that, like Moderately Armored, this feat could also be bypassed through clever multiclassing. If, for example, you started with a Fighter dip as your first level, you’d get both the Constitution proficiency and all the armors. Multiclassing truly does open up the full power of a character.
  • ChefTCoE: Calamari, anyone? Jokes aside, it’s not a bad option when you’re evening out an odd Constitution score. And who can pass on the flavor of offering the party a taste of what the deep has to offer, in a manner of speaking at least. There is at least a bit of selfish motivation here. By making short rests even better, we encourage the party to maybe take an extra one each adventuring day. For Pact Slots. Genies get that ten minute bottle trick, but we have to cook and eat stuff.

The Fathomless Armor and Weapons

Under normal circumstances, Fathomless Warlocks have the same Light armor proficiency as base Warlocks, and will be looking to get some Studded Leather. If you’ve gotten Medium proficiency, either through multiclassing or Moderately Armored, then you’ll be looking for Half-Plate, similar to a Hexblade.

Weapons, on the other hand, are not in the Fathomless’ interest. Keeping an open hand for somatic components is useful, and if you happen to be holding a shield, the best option for that is having a component pouch over having a spell focus (unless you find a magic one but then you have to start juggling or take Warcaster).

Example Fathomless Warlock Build – Never Safe From Water

This build focuses on using the Tentacle of the Deeps feature to add a bit of zoning and control in combat. The damage isn’t much, but it’s a good use of our bonus action and helps stretch out spell slots by saving on having to cast Hex as often as other Warlocks. Additionally, we make some unconventional feat choices to increase our own personal protection without resorting to multiclassing. I think the build turns out fine this way. Taking a Fighter dip would have eaten at least one ASI while making up for two feat choices.

As for what we actually do in fights, put down the Tentacle and smack people while also using Repelling Blast to push them around. The combination of stealing their movement speed and forced movement should keep your foes away from your team and inside wherever you tell them to be, likely inside some sort of controlling or damaging AoE. Coordinate with your team to save on spell slots by supplying such spells when Tentacle is ready for action and tagging out to use Hex instead when it’s too spent for the day.

Abilities

We’re going to pick Variant Human and take Moderately Armored at first level, which includes a +1 to Dexterity and will be reflected in the chart. We’ll also be putting a +1 into Constitution and Charisma. Because we only need 14 Dexterity for Medium Armor, we have extra points left over which we spend on Intelligence since we’ll be taking the Arcana skill.

BaseIncreasedLevel 20
Str888
Dex131414
Con151620
Int121212
Wis888
Cha151620

Race

Mentioned above, we’re taking Variant Human for access to the bonus feat. We’ll also get a bonus skill proficiency, choosing Arcana. The bonus language is more campaign dependent, but for flavor I’ve chosen Deep Speech.

Background

For a background, I’ve taken Entertainer, partly for fun and partly for usefulness. Acrobatics along with our bit of Dexterity will keep us out of grapples without cutting into your limited spell slots to teleport and help us wriggle our way through tight situations. Performance and an Instrument may sound redundant, but together those combine into Advantage on those kinds of checks if you’re using the rules presented in Xanathar’s. Handy for making extra coin during downtime.

Skills and Tools

We’ve got Deception and Intimidation from Warlock, Arcana from Human, and Acrobatics, Performance and any musical instrument from Entertainer. We eventually also gain Cook’s Utensils from the Chef feat, but could just as easily take Skill Expert to gain Persuasion and Expertise in whatever seems useful.

Feats

I’ve explained above in the feats section how each of the feats fit in this build so I’ll just briefly list out the levels where they go.

At first level, Variant Human grants a bonus feat and we take Moderately Armored, gaining proficiency in Medium Armor and Shields as well as a +1 to Dexterity, allowing us to start with 14 Dexterity.

At fourth level, we take an ASI for +2 Charisma, going from 16 to 18, improving our spell attacks and spell DCs.

At eighth level, we take another ASI for +2 Charisma, capping at 20. We do have the option of swapping this around with Resilient (Constitution) at twelve, but only do that if you expect to have to make Constitution saves outside of Concentration. We can just take the Eldritch Mind invocation for now and trade it out later when we get Resilient.

At twelfth level, we take Resilient (Constitution), gaining save proficiency and adding +1 Constitution, going from 16 to 17.

At sixteenth level, we’re taking Chef to improve the benefits of short resting to encourage the party to get an extra one in each day for the benefit of our Pact Magic slots. We also gain another +1 to Constitution, going from 17 to 18.

At nineteenth level, we’re taking an ASI for +2 Constitution, capping at 20.

Levels

LevelsFeats and FeaturesNotes and Tactics
1Bonus Feat: Moderately Armored

Patron: Fathomless
-Tentacle of the Deeps
-Gift of the Sea

Pact Magic – 1 Slot
-Cantrips
–Eldritch Blast
Mage Hand
-1st-level Spells
–Armor of Agathys
–Hex (c)

Skills
-Acrobatics
-Arcana
-Deception
-Intimidation
-Performance
For starting equipment, it’s possible to roll for money and get what we need, since we’ll need 50 GP for Scale Mail, 10 GP for a shield, and 25 GP for a Component Pouch, but I suggest talking with your DM and asking if they mind you just getting Scale Mail as starting gear like other classes that have proficiency by default.

We get two cantrips and two 1st-level spells at first level.
Eldritch Blast is our big reason for being a Warlock. Really important for blasting our foes in the face.

Mage Hand is a useful spell for doing small things and we can even say it looks like a tentacle when we cast it.

We only get one slot at this level, and Hex lasts an hour so it’s really useful. Armor of Agathys also lasts an hour so it makes another good choice.

The Fathomless Patron grants us Tentacle of the Deeps and Gift of the Sea.

We only get two uses of the Tentacle each day, so don’t waste it but also don’t forget to use it.

Gift of the Sea is just a swim speed and water breathing. It’s nice when it comes up, and if we can make use of it that’s great, but it’s not the end of the world if it’s not relevant because it’s more of a ribbon feature unless you’re in an aquatic campaign.
2Invocations
-Agonizing Blast
-Repelling Blast (Devil’s Sight)

Pact Magic – 2 Slots
-1st-level Spell
–Thunderwave
-Or-
–Arms of Hadar
Agonizing Blast and Repelling Blast are the key components of forcefully blasting people for fun, profit, and tons of damage. Remember that the same bonus action to tentacle smack someone also allows the tentacle to teleport up to 30 feet before the attack. As long as we don’t repel someone more than 40 feet away from the tentacle, they can be smacked. Alternatively, nothing prevents us from smacking first and repelling later.

Really, you’ll find it’s more important to repel targets into things that can’t move, like Webs or Walls of Fire or Black Tentacles.

We could take Devil’s Sight early and leave Repelling for later if we really need the Darkvision now.

Thunderwave is an AoE spell we get from the Fathomless expanded spell list. While it is a Constitution save, it’s a nice source of pushing targets and the damage isn’t bad.

Optionally, Arms of Hadar is a little more area radiating out from us for less damage, but vs a Strength save and robbing targets of their Reactions instead of pushing them.

I think Thunderwave is easier to aim, but Arms of Hadar is fine if that’s your preference.
3Pact Boon
-Pact of the Talisman

Pact Magic
-2nd-level Spell
–Invisibility (c)
-Retrain
–Thunderwave –> Shatter
For our Pact Boon, we take the Pact of the Talisman. Right now it grants a bonus to ability checks when worn, but later we’ll have Invocations to beef it up more.

For spells, we trade Thunderwave out for Shatter. Same damage (because of how Pact Magic works), smaller area, but better range.

We also learn Invisibility, which is pretty useful for a lot of things.
4ASI: Charisma +2 (16=>18)

Pact Magic
-2nd-level Spell
–Hold Person (c)
-Cantrip
Prestidigitation
We boost our Charisma to keep up our Spell Attacks and DCs.

Hold Person is a great spell for messing up Humanoids. Paralysis is just really strong.

We don’t really need more damage from Cantrips, so we’ll take Prestidigitation because it has many wonderful uses.
5Invocation
-Devil’s Sight (Repelling Blast)

Pact Magic
-3rd-level Spell
–Hypnotic Pattern (c)
Devil’s Sight will help us see with our terrible Human eyes. Necessary for those deep sea dives.

Hypnotic Pattern, with a quick flash of writhing visions, can knock a lot of foes out of the fight at once. Even if some of them spend actions to shake their allies free, that’s costing actions to not hurt our party.
6Guardian Coil

Oceanic Soul

Pact Magic
-3rd-level Spell
–Counterspell
Guardian Coil is a nice reaction ability that lets us reduce incoming  damage if the target is close to the tentacle.

Oceanic Soul gives us cold resistance, which is nice, and a form of Tongues that functions when you’re underwater, which is kinda neat.

Counterspell is nice insurance against enemy spellcasters.
7Invocation
-Lance of Lethargy

Pact Magic
-4th-level Spell
–Banishment (c)
Lance of Lethargy is another piece to the oppression of the Tentacles. Hitting with both the Tentacle and Eldritch Blast now robs a target of 20 feet of movement.

Banishment puts someone somewhere safe and away from here for a minute. Cuddled by Tentacles counts as safe. I think.
8ASI: Charisma +2 (18=>20)

Pact Magic
-4th-level Spell
–Shadow of Moil (c)
More Charisma, maximum power.

Shadow of Moil gives us concealment and other benefits. It doesn’t have to look like fire, we could be concealed by a wriggling mass of slimy arms.
9Invocation
-Protection of the Talisman

Pact Magic
-5th-level Spell
–Synaptic Static
Protection of the Talisman boosts up the Talisman to assist with Saving Throws as well.

What might not be obvious about this Invocation is that there are two separate pools of uses for the Ability Check and Save bonuses.

Synaptic Static does some good damage with a great saving throw and a no-concentration debuff that messes up attacks for a minute. Overall great spell.
10Grasping Tentacles
-Black Tentacles

Pact Magic
-Cantrip
–Blade Ward
We not only learn Black Tentacles, but also it’s far stronger for us. Not only does it grant free Temporary HP when we cast it, our Concentration on this spell can’t be broken by damage.

Blade Ward is for when we’re Concentrating on something but we don’t expect Dodging to be enough. In those cases, taking half damage will require a lower DC for the Concentration Save.
11Mystic Arcanum 6
-Soul Cage

Pact Magic – 3 Slots
-5th-level Spell
–Bigby’s Hand (c)
Who left all these souls lying around? Oh well, ours now.

They go nice with this big floating Tentacle that smacks people. Like our other Tentacle, but Bigby-er.
12Feat: Resilient (Constitution)
+1 CON (16=>17)

Invocation
-Rebuke of the Talisman
Time to shore up those Constitution saves for those Concentration saves.

Rebuke of the Talisman is another reaction ability to defend against attacks, similar to the Guardian Coil. While it may seem we have competing reactions, there are still going to be fights without the Tentacle and this helps with those.

Keep in mind the range of this; the attacker must be within 30 feet of us, not the bearer of the Talisman.
13Mystic Arcanum 7
-Forcecage

Pact Magic
-3rd-level Spell
–Fear (c)
Forcecage. Put someone in a timeout box while the grownups are talking.

Fear is a neat control spell. It’s actually much better when only half of the foes fail the save and start running so one tough fight becomes two easier fights.
14Fathomless PlungeThis is a limited teleportation ability. If there is a convenient body of water nearby for using this it’s good, but on the average we’ll have trouble using this unless you’re actively in water or you’re in a place like Minnesota where you’re perpetually and inexplicably adjacent to a body of water.

I don’t have much advice for making this work if there isn’t already convenient water in the area.
15Mystic Arcanum 8
-Glibness

Invocation
-Shroud of Shadow

Pact Magic
-4th-level Spell
–Sickening Radiance (c)
-5th-level Spell
-Retrain
–Invisibility –> Hold Monster (c)
Of course Tentacles are your friends, and, while Glibness is running, you’ll believe me.

At-will Invisibility is a very nice Invocation. We’ll replace knowing Invisibility with extra spells.

Sickening Radiance is just good, but so are a lot of other options, which is why we waited to get it this long.

Hold Monster is also strong and worth picking up since we’re dropping Invisibility.
16Feat: Chef
+1 CON (17=>18)
Chef is a great way to subtly encourage people to have more Short Rests each day so we can be far stronger.
17Mystic Arcanum 9
-Foresight

Pact Magic – 4 Slots
-5th-level Spell
–Far Step (c)
Foresight is a very strong option, giving 8 hours of Advantage on everything while imposing Disadvantage on incoming Attacks.
Be selfish with this toy, it’s so much fun.

Far Step is basically Misty Step but every turn for a minute. We’re picking it up in anticipation of the next Invocation.
18Invocation
-Bond of the Talisman
Bond of the Talisman allows someone else to Teleport to us (or vice versa) if they wear the Talisman.

Combine this with Far Step to quickly zip yourself and a partner quite a distance.
19ASI: +2 Constitution (18=>20)

Pact Magic
-5th-level Spell
–Dream
Capped Constitution. Good timing.

Dreams are a fun way to communicate. Especially when they’re full of friendly wriggly Tentacles. Frientacles.
20Eldritch MasterGet our spells back with a quick minute of focus. It’s not a bad capstone. More spells is never bad.