Magus Handbook: PF2 Class Guide

Introduction

Following the tradition established by DnD 3.5’s Duskblade, the Magus is a medium-armored hybrid martial caster. Their signature feature, Spellstrike, allows you to deliver spells at the end of a weapon, combining the damage of your weapon with the damage of a spell. However, in exchange for this exceptional martial capability you give up much of the versatility and magical might of a typical spellcaster.

With a huge amount of damage output, the Magus is a natural Striker. They lack the built-in durability and “stickiness” of a Defender, but with the right subclass and if you take the Attack of Opportunity feat, you can come to class to matching the Fighter’s capacity as a Defender. The Magus needs high Intelligence to back up their spells, so the Magus also makes a natural Scholar, covering the party’s need for knowledge skills. Depending on your build you could also serve as a Scout, but the Magus won’t match a rogue and the Magus doesn’t have the Wizard’s magic to fill the gap. Your limited spellcasting also means that you’re not an effective support or utility caster, so the Magus fills a role similar to the Fighter, but without the Fighter’s durability.

The Magus’s spellcasting is extremely unusual. You prepare spells from a spellbook just like a wizard, but you have at most 4 regular spell slots (not counting Focus Spells), split between the two highest-level spells you can cast. In a way, this feels similar to DnD 5e’s Warlock. The Magus also gets a few lower-level slots from Studious Spells which can be used for a handful of specific buff spells, but these are few in number and limited in scope. The Magus also never gets 10th-level spells.

Because leveled spells present an opportunity for a big power spike, the Magus benefits greatly from additional sources of spell slots. Archetypes, scrolls, and staves are all extremely useful for the Magus.

You may also find these supporting articles helpful:

Disclaimer

RPGBOT uses the color coding scheme which has become common among Pathfinder build handbooks.

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.

Magus Class Features

Key Ability: Strength or Dexterity. For a martial class that’s perfect.

Hit Points: 8+ won’t compete with durable front-line martials like the Fighter.

Proficiencies: Your proficiencies aren’t as impressive as the Fighter’s, but you make up for it with magic.

Perception: Below average Perception, and with little dependence on Wisdom your Perception will likely be poor.
Saving Throws: Good Fortitude and Will saves, middling Reflex saves. Dexterity-based builds will have excellent saves across the board.
Skills: 3+ skills from your class at first level and standard increase progression. With high Intelligence you should start with plenty of Trained skills.
Attacks: Simple and Martial weapons, and typical proficiency progression for martial classes like the Barbarian and the Ranger, but you don’t get weapon critical specialization effects from the Magus.
Defenses: Only up to medium armor, but your proficiency progression is as good as the Fighter, placing you among the best in the game. You never get armor specialization effects.
Spell DC: Your spellcasting proficiency won’t increase as quickly as the Wizard’s. You also don’t have a class DC to use as a basis for Weapon Critical Specialization Effects, so if you find a way to get access to them, you’ll need to stick to weapon types that don’t allow a save.

Arcane Spellcasting: Similar to the Wizard, the Magus uses the Arcane spell list, and they are prepared spellcasters so you need to prepare a spell in each of your spell slots during your Daily Preparations. However, the Magus’s spell slots work very differently from other classes. Rather than accumulating a growing number of slots across your full range of spell levels, the Magus maxes out at 4 spell slots of two spell levels (not counting Studious Spells).

Heightened Spells: Heightening spells is an important mechanic in Pathfinder 2e. Many important spells scale with spell level, allowing them to stay relevant long after you first learned them. Since the Magus doesn’t use a Spell Repertoire, you only need to learn a spell once, then you can prepare it at any level that you can cast.
Cantrips: The Magus can prepare 5 cantrips, and they start with 10 in their spellbook so you have lots of room to customize your arsenal every day. Cantrips will do a lot of work with Spellstrike, so cantrips are a much more central part of your spellcasting than they are for most spellcasters.
Spellbook: Your spellbook is your most valuable possession. Guard it jealously; if you lose it, you’ll be unable to prepare spells. You don’t need to hoard new spells quite like a wizard does, but you likely still want to learn more spells than what you get for free.

Spellstrike: Spellstrike is the Magus’s central feature, and much of how you build your character will be to get the most out of Spellstrike. To briefly summarize: you cast a spell and hit your target with a weapon in order to deliver the spell, combining the damage of both. If you choose to ignore Spellstrike, you’re basically just a disappointing fighter.

Because Spellstrike is so central to the class, let’s really dig into how it works and how it fits into playing the class. Understanding the action economy, the recharge mechanics, and how Spellstrike works with your spells will make you much more effective. The book draws attention to this issue in the “Combining Your Abilities” sidebar, and you know it’s complicated when the rules text gives you hints on tactics.

Using Spellstrike is a 2-Action activity. It typically uses your melee reach, but Starlit Span offers ranged weapons as an option. Using Spellstrike counts as two attacks for your Multiple Attack Penalty, so making additional strikes in the same turn is generally both difficult and ineffective. If you score a critical hit, you score a critical hit with both the weapon attack and the spell. Of course, that also means that it’s very “hit or miss” and since you’re unlikely to make additional strikes in the same turn you really need Spellstrike to hit.

Your choice of spell is crucial, and you want to have enough options available to cover whatever you might face. That’s hard to do with at most 4 spell slots, so you need to lean heavily on your cantrips. You’re limited to spells which make spell attacks, but some class feats can expand that and we’ll discuss tactics in the assessments for those feats. Gouging Claw (published in Secrets of Magic (affiliate link)) is your go-to option, providing good damage, good scaling, and an excellent critical hit effect. If you use anything else with Spellstrike it needs to beat Gouging Claw to justify consideration.

Recharging Spellstrike is easily the most challenging part of playing the Magus. You want to use Spellstrike as often as possible, but you need to do something to recharge it after each use, and this will typically require spending an Action of some kind. You can just spend an Action to recharge, but that effectively turns Spellstrike into a 3-Action activity, and while Spellstrike is really good, that’s a steep action cost. More likely, you’ll recharge it by casting a Conflux Spell (the Magus’s Focus Spells). The options in Secrets of Magic all cost one Action, so you can reliably use them at no extra Action cost in order to recharge. You can also recharge with certain class feats, including Magus’s Analysis and Rapid Recharge. These options are important because your Focus Pool is limited in size, so you may not have enough Focus Points to keep recharging.

Positioning is an immediate problem for the Magus. The 2-Action cost plus the Action cost to recharge means that you typically can’t move, recharge, and use Spellstrike on the same turn. Generally that means that you can expect to use Spellstrike once every other turn unless you’re using the Starlit Span Hybrid Study so that you can attack at range. Using Reach weapons can mitigate this somewhat, as can the Laughing Shadow’s Dimensional Assault. But for everyone else, if you need to move to get to a new target you likely need to give up Spellstrike for a turn.

Once you gain the ability to cast Haste, this all improves somewhat. An extra Action which you can use to Stride makes things much easier. You can’t Step with this action, but if you’re in a position where Step makes sense you’re probably in melee already, so you can go straight to hitting stuff.

Arcane Cascade: Oh great, another action cost. The damage bonus is pitifully small even with the scaling, so it’s basically only there to make you feel good and if you’re very lucky to trigger vulnerabilities. On its own, this is not worth the action cost.

Arcane Cascade’s real benefit comes from your Hybrid Study. You’ll get an additional benefit which applies only while you’re in Arcane Cascade, and the benefits are generally good.

The specific wording of Arcane Cascade is fundamentally broken: using the Action to activate the stance breaks the stance because you no longer qualify for the stance. We’ve been promised errata, but haven’t recieve it as of this writing. I believe the intent is for the stance to last until the end of the encounter, and I’m going to write the rest of this handbook with that assumption in mind.

Hybrid Study: See my Magus Hybrid Study Breakdown.

Conflux Spells: See magus focus spells, below.

Magus Feats: See magus feats, below.

Studious Spells: Two additional spell slots. You can only use them for a handful of buff spells, but the options are mostly good and they cover some essentials which allow the Magus to function at high levels without the assistance of another spellcaster.

Double Spellstrike: This essentially doubles how much you can get out of your spell slots. Considering that you’re casting 8th and 9th-level spells at this level, that’s a lot of extra firepower.

Magus Ability Scores

Strength-Based

Inexorable Iron and Twisting Tree builds will typically need to be Strength-based, though there are a few two-handed Finesse weapons so Inexorable Iron can be built around Dexterity.

Str: Your key ability score.

Dex: You need 12 to fill out medium armor, but that’s all.

Con: Fortitude saves and hit points.

Int: Powers your spellcasting to some degree, but since you’re delivering spells at the end of a weapon attack you typically don’t need your spellcasting ability to be as high as a full caster. However, if you plan to rely on spells that you can’t put behind an attack roll (fireball, etc.) you still need the Intelligence to back it up.

Wis: Will saves, Perception, Nature, and Religion. If you’re planning to rely on Raise a Tome, you’ll need a bit of this, but make sure you get your Dexterity to 12 first.

Cha: Dump.

Dexterity-Based

If you plan to use Finesse weapons or fight at range, build around Dexterity.

Str: If you’re going to fight in melee or use a Propulsive weapon, you want a little bit for the extra damage, but your damage output comes primarily from Spellstrike, so don’t strain yourself to get one or two more points of damage from your Strength.

Dex: Your key ability score.

Con: Fortitude saves and hit points.

Wis: Will saves, Perception, Nature, and Religion. If you’re planning to rely on Raise a Tome, you’ll need a bit of this, but make sure you get your Dexterity to 12 first.

Cha: Generally this is your dump stat, but the Laughing Shadow needs a bit to support feinting.

Ancestries

Your choice of Ancestry is frequently a very important build for many classes, but for the Magus it can often be an absolutely defining build decision. Because the Magus can be built around either Strength or Dexterity, whichever of the two is easier to boost is one in a series of benefits which can greatly influence your build. Avoid Intelligence Flaws, but otherwise you can do fine with many races.

For a magus planning to fight unarmed, look for an Ancestry that can get you a better unarmed attack or consider a Versatile Heritage which can get you one, such as the Changeling’s Hag Claws ancestry feat. The Arcane Fist class feat is the Magus’s only built-in option if you want to fight unarmed, and it is outright inferior to whatever option you can get from your Ancestry.

For a magus planning to use a weapon, weapon familiarity feats are a great choice. The Magus doesn’t get access to Critical Specialization Effects (with the exception of the Student of the Staff class feat), so getting it from your Ancestry is helpful. Unfortunately that does limit you to a small set of weapons, but those weapons are often very good. When considering what weapons to use, be sure to consider the advice under Magus Weapons, below.

Access to innate spellcasting from your Ancestry can also be very helpful. While the Magus can prepare as many cantrips as other spellcasters and gets access to the Cantrip Expansion feat, your limited pool of spell slots means that you don’t have as many magic options as most spellcasters. Adding an extra cantrip or a leveled buff spell can expand your options significantly. However, remember that innate spells are typically Charisma-based, so you don’t want anything that cares about a spell attack or a saving throw. Stick to utility spells, buffs, and defensive options.

Catfolk^APG: Use the Optional Flaw rule to dump Charisma in exchange for another Boost so that you can boost Dex/Con/Int. Catfolk Weapon Familiarity can get you access to the Whip Claw, and you can get a good natural weapon from either the Clawed Catfolk Heritage or from Saberteeth if you want to build an unarmed magus. Catfolk Weapon Rake gets you Critical Specialization Effects, but the Brawling category (which is typically what you use for unarmed strikes, including the Catfolk’s claws/teeth) relies on your Class DC, and the Magus doesn’t have one. In many ways, the Catfolk’s options resemble worse versions of the Gnome’s, with the exception of unarmed strikes.

Dwarf^CRB: With high ancestry hit points and Mountain’s Stoutness, the Dwarf is very durable, making them a great option for front-line builds like Inexorable Iron and Sparkling Targe. Dwarven Weapon Cunning gets you access to critical specialization effects with a few weapons, but your only two-handed option is the Dwarven Waraxe, so Inexorable Iron’s options aren’t fantastic. Consider using the Optional Flaw rule to dump Wisdom in exchange for an Intelligence Boost.

Elf^CRB: Dex and Int boosts are great, but low ancestry hp and a Constitution Flaw make melee builds hard, so you’re likely going to stick to Starlit Span and use a bow. You can take Elven Weapon Familiarity to get access to the Elven Branched Spear, which is a bit like an upgraded whip, but melee is still hard. Elven Weapon Elegance offers access to critical specialization effects with bows and elven weapons, so if you went either route you’re in good shape.

Gnome^CRB: Use the Optional Flaw rule to dump Charisma in exchange for another Boost so that you can boost Dex/Con/Int. Gnome Weapon Familiarity is hard because all of your best weapon options are Strength-based and the Gnome has a Strength Flaw which is too costly to reverse. Instead, build around Dexterity and look at other feat options. The Wellspring Gnome Heritage and First World Magician both get you additional cantrips, Animal Accomplice gets you a familiar, and eventually First World Adept can get you some additional innate spells.

Goblin^CRB: The Goblin offers surprisingly little. Goblin Weapon Familiarity gets you access to the Dogslicer, which is mildly useful for the Laughing Shadow, but not so good that it makes a big difference. Burn It! can make Produce Flame a more effective go-to cantrip for Spellstrike, but Gouging Claw will still be more effective since fire damage resistance is so common.

Halfling^CRB: Use the Optional Flaw rule to dump Charisma in exchange for another Boost so that you can boost Dex/Con/Int. Halfling Weapon Trickster gets you Critical Specialization Effects with the Shortsword and the Sling Staff, but the Sling Staff relies on your class DC, and the Magus doesn’t have one. That essentially limits you to the shortsword, and there’s little else from the halfling the that’s directly helpful for the Magus.

Human^CRB: Fantastic and versatile. Natural Ambition can get you access to another of the Magus’s excellent 1st-level feats, and Unconventional Weaponry can get you access to cool weapons like the Gnome Flickmace. Unfortunately, the Human doesn’t offer much beyond their 1st-level Ancestry Feats.

Kobold^APG: The Kobold’s boosts and flaws strongly resemble that of the Elf, and like the Elf, your best bet is to fight at range. You don’t get any good weapon options with Kobold Weapon Familiarity, so stick to generally useful options like Grovel and Cower. Eventually, you can get Dracomancer. Spellscale Kobold can get you an extra cantrip and Strongjaw Kobold can get you an unarmed strike. The Kobold Breath feat tree is tempting, but too hard to fit into your action economy consistently.

Orc^APG: Very similar to the Dwarf for the Magus’s purposes. Decent for a Strength-based melee build. Tusks can get you a better unarmed strike, but Bloody Blows is redundant with Gouging Claw so it’s not worth the feat. Orc Weapon Familiarity can get you the Butchering Axe and Orc Weapon Carnage can get you Critical Specialization Effects with it.

Ratfolk^APG: Perfect boosts for a Dexterity-based build, but not a lot of feat options.

Tengu^APG: Great boosts, and you can use the Optional Flaw rule to get a third if you want it. Tengu Weapon Familiarity gets you access to the Katana and the Temple Sword, though neither is significantly better than the Longsword or the Rapier. You do get to pick two other swords, but that won’t get you anything that the Magus doesn’t get anyway. Tengu Weapon Study gets you Critical Specialization Effects, including the two additional swords which you picked with Tengu Weapon Familiarity, so you can get it with the Longsword and/or the Rapier. The Dogtooth Tengu Heritage and Dogfang Bite give you an unusually effective unarmed strike.

Backgrounds

You generally want boosts to your Key Ability Score (Strength or Dexterity) and either Constitution or Intelligence.

If you’re having trouble deciding, here are some suggestions:

Academy Dropout^SoM
Scholar^CRB
Student of Magic^SoM

Magus Skills and Skill Feats

You get Skill Increases at 3rd and 5th level to raise skills to Expert, increases at 7th, 9th, 11th, and 13th level to raise skills to Master, and increases at 15th, 17th, and 19th level to raise skills to Legendary. That means that you can maximize at most three skills, and the rest of your skills might not advance beyond Trained.

You get Skill Feats at even-numbered levels, giving you a total of 10 Skill Feats (and maybe another from your Background) by 20th level. Generally, you want to invest these feats in the same skills which you are choosing to maximize, though in some cases you may want to grab feats from skills which don’t require that you be more than Trained.

Acrobatics (Dex): Only situationally useful until you learn to fly, and even then it’s likely enough to be Trained.
Arcana (Int): If you plan to use Magus’ Analysis, this is absolutely essential.
- Arcane Sense^CRB: Save yourself a cantrip.
- Unified Theory^CRB: Save yourself the trouble of increasing Occultism, Nature, and Religion, plus you get to use your Intelligence modifier and whatever else you’ve done to optimize your Arcana modifier (items, etc.).
Athletics (Str): Even if you’re built around Strength, Athletics can be a hard choice. The Magus’ action economy is already challenging, and spending actions to grab or shove creatures is hard to justify. You might be Trained for stuff like climbing and jumping, but don’t expect to use this in combat.
Crafting (Int): You have the Intelligence to make Crafting very effective. If you’re going for Sparkling Targe, this is essential for repairing your shield/book/shieldbook/bookshield.
Deception (Cha): Charisma is the Magus’ only safe dump stat, but the Laughing Shadow relies on Feint, so if you’re a Laughing Shadow you need Charisma and you need to invest in Deception. Unfortunately, Distracting Spellstrike doesn’t benefit from anything that improves the effects of Feint, so there’s no unique benefits to investing in Deception skill feats.
Diplomacy (Cha): Charisma is the Magus’ only safe dump stat.
Intimidation (Cha): Charisma is the Magus’ only safe dump stat.
Lore (Int): Too vague, too specific, too numerous.
Medicine (Wis): Someone in your party needs it, but hopefully that someone has more Wisdom than you.
Nature (Wis): Essential if you plan to use Magus’ Analysis.
Occultism (Int): Essential if you plan to use Magus’ Analysis, and you have the Intelligence to make it work, so even if you’re not using Magus’ Analysis you should strongly consider at least being Trained.
Performance (Cha): Charisma is the Magus’ only safe dump stat.
Religion (Wis): Essential if you plan to use Magus’ Analysis.
Society (Int): The closest you’ll get to a social skill.
Stealth (Dex): If you’re built around Dexterity you can be good at Stealth.
Survival (Wis): Too situational.
Thievery (Dex): Someone in your party needs to be good at this, and if you’re built around Dexterity you’re a decent candidate.

Magus General Skill Feats

Recognize Spell^CRB: If you plan to use Magus’ Analysis, you already have all the skills that you need to support this. Even if you don’t use Magus’ Analysis, being Trained in each of the four relevant skills is easily achievable.

Magus Feats

Class Feats

1st Level

Arcane Fists^SoM: Get natural weapons from your race. They’ll almost certainly be more effective than this.
Familiar^SoM: Familiars are awesome, but the Magus doesn’t have space in their action economy to spend actions commanding their familiar.
Magus’s Analysis^SoM: This is good, but it’s a gamble. If you fail the check, your action is wasted. You need to invest skill increases in arcana, nature, occultism, and religion to make sure that you can always use this, and even then you can’t guarantee success. If it works, this is certainly better than just spending an action to recharge Spellstrike, but the fact that you can fail should heavily influence your decision.
Raise a Tome^SoM: The stats for your book match those of a wooden shield, and while that’s fine at low levels it won’t scale.
Do not use your spellbook for this. DO NOT USE YOUR SPELLBOOK FOR THIS.

2nd Level

Cantrip Expansion^SoM: More cantrips means more options to combine with Spellstrike. Not essential, but an easy go-to option.
Enhanced Familiar^SoM: Making your familiar better won’t solve your action economy problems.
Expansive Spellstrike^SoM: The Magus’ best option for handling crowds, and this allows you to expand your spell options beyond buffs and spells which make attack rolls. Be extremely cautious about bursts unless you’re using the Starlit Span Hybrid Study because bursts will frequently include you in their area, and don’t use spells that target a number of creatures (unless that number is one) because you only get to target one creature with your Spellstrike. And remember that your save DC won’t match a real wizard.
The interaction with Reach weapons and with Starlit Span is odd. You get to pick any square adjacent to the target as the origin point for cones/lines, so you’re free to make those AOEs point in weird directions like straight back toward you.
Force Fang^SoM: Increasing your Focus Pool size means that you can use Conflux Spells to recharge Spell Strike more often. Force Fang is also a decent spell, so if your Hybrid Study’s Conflux Spell isn’t working for you, Force Fang is easy to fit into any build.
Spell Parry^SoM: You need a free hand, which means that this is mostly for Laughing Shadow. The +1 bonus is consistently useful, but I don’t know if it’s good enough for the feat and action costs. It’s almost certainly better than using a weapon with Parry, but you can also learn the Shield spell which has the same Action cost. Sure, a Parry weapon and the Shield spell won’t give you a +1 to saves against spells targeting you, but you need to weigh those opportunity costs.
Spirit Sheath^SoM: Too situational.

4th Level

Devastating Spellstrike^SoM (Inexorable Iron): This isn’t a lot of damage, but it’s guaranteed damage with no save against an unlimited number of possible targets, and it specifically only affects foes, so you can easily drop this on enemies even if they’re in melee with one of your allies. You can also use spells which deal splash damage (Acid Splash, etc.) and the splash damage from the spell is added to the splash damage and applied with no save.Your enemies will likely figure this out quickly and stop clustering together, but if you’re being swarmed in melee that might be exactly what you want..
Distracting Spellstrike^SoM (Laughing Shadow): Feint can make your target Flat-Footed, which reduces their AC by 2, which has a 1 in 5 chance of increasing your degree of success. This doesn’t add any extra Action cost, it doesn’t require complex tactical thinking, and as long as you can invest a bit in Deception this can be consistently useful.
Emergency Targe^SoM (Sparkling Targe): Since this consumes your Reaction you can’t use Shield Block, but honestly that’s fine. Fitting in the Action to Raise a Shield can be difficult for the Magus, and this dramatically reduces that tax on your action economy. The circumstance bonus applies to the triggering attack, so you have a 1 in 5 chance to reduce the attack’s degree of success, potentially negating a hit or turning a critical hit into a regular hit. You’re still using the Raise a Shield action, so the bonus stays in place until your turn just as if you had used Raise a Shield on your own turn.
Starlit Eyes^SoM (Starlit Span): Unless your DM really likes to use Concealment, Shooting Star should be sufficient.
Steady Spellcasting^SoM: Not reliable enough. If you make this check you have a 3 in 10 chance of success.
Striker’s Scroll^SoM: A great way to get some extra leveled spells to use with Spellstrike, provided that you can pay the cost to buy or craft enough scrolls to keep this useful. You also need to strike a balance between spending too much money and conserving your scrolls to the point that you shouldn’t have taken the feat. If you’re the sort of person who hoards consumable items to the end of a video game, skip this.
Student of the Staff^SoM (Twisting Tree): Crucial for Twisting Tree. A magic staff is a great source of additional leveled spells, allowing you to perform those big power spikes more often and to expand your available pool of leveled spells. The challenge you would normally run into is that you need to hold the staff to use it, and holding a staff in each hand is going to become a problem which this neatly solves. You also get critical specialization effects, which the Magus normally can’t do, and you add Deadly d6 to your staff. This feat is really good.

6th Level

Attack of Opportunity^SoM: Excellent on any melee character.
Cascade Countermeasure^SoM: See Magus Focus Spells.
Knowledge is Power^SoM: This is a good improvement if you plan to use Magus’ Analysis, but otherwise I wouldn’t bother. Tracking the effect of the feat is massively annoying since it provides three distinct single-use benefits to each member of your entire party.
Shielded Tome^SoM: Ask yourself “why do I need to have a book in my hand?” and “is that important enough that I have now spent two class feats for this novelty?” and then email me if you have a good answer because I haven’t come up with one.

8th Level

Capture Magic^SoM: You want to get into Arcane Cascade as quickly as possible in combat, so unless you get hit with a spell before your first turn, the only consistent benefit is the +2 damage bonus which you’re likely only going to apply once each time you activate this.
Fused Staff^SoM: Staffs are a great way for the Magus to get additional leveled spells, and Twisted Tree has had a monopoly on using magic staffs until this point.
Runic Impression^SoM: See Magus Focus Spells.
Spell Swipe^SoM: 3 actions, melee only, the targets need to be adjacent, and if you use a regular Spellstrike with an attack spell, it still only affects one target. In most cases, this is just an extra Strike against another creature and you don’t apply the Multiple Attack Penalty until this 3-Action activity is done, at which point your turn is probably over. This is good if you can make it work, but it’s very difficult to set up.
Standby Spell^SoM: Buy a scroll or a magic staff if you want to have more options for what spells you can cast in a day.

10th Level

Cascading Ray^SoM: A decent way to get some extra damage, but the action economy may be hard. The damage is similar to many cantrips which take 2 Actions to cast.
Dazzling Block^SoM (Sparkling Targe): Amazing crowd control. You should work to use this as much as possible.
Dimensional Disappearance^SoM (Laughing Shadow): Use Spellstrike, then use Dimensional Assault to teleport and turn invisible. On your next turn, use Dimensional Assault again while you’re invisible. Repeat until you run out of Focus Points or your target moves and you need to walk around.
Lunging Spellstrike^SoM (Twisting Tree): Not always useful, but this could easily save you some actions spent moving, and if you have a magic staff you likely have plenty of suitable spells to trigger this.
Meteoric Spellstrike^SoM (Starlit Span): The damage is too small and having creatures between you and the target means that your target likely has cover.
Rapid Recharge^SoM: Helpful, but once per day isn’t going to suddenly solve all of your problems.
Sustaining Steel^SoM (Inexorable Iron): Not a lot of healing considering that the Magus gets so few spell slots.

12th Level

Conflux Focus^SoM: Using Conflux Spells to recharge your Spellstrike is a central tactic, so this is crucial to remaining effective throughout an adventuring day.
Magic Sense^SoM: Neat, but you can get Detect Magic from the Arcane Sense trait and the vast majority of magical things can wait to be scrutinized until after combat. I think the intent here is to help you find magically concealed enemies, but that’s too situational to justify the feat.
Overwhelming Spellstrike^SoM: Since the Magus has so few spell slots, simply choosing to use a different spell to get around resistances isn’t always a choice. Gouging Claw deals slashing damage and persistent bleed, so those are fine, but for your leveled spells this is great.

14th Level

Arcane Shroud^SoM: You’re going to use Arcane Cascade anyway, and this gets you some more mileage out of that Action to activate the stance. Many of the spells are very good, but coordinating the spell you cast to trigger this will take some effort. It’s not stated, but I assume that you get the benefits of these spells at their lowest level.
Hasted Assault^SoM: See Magus Focus Spells.
Preternatural Parry^SoM: Broadly and consistently useful. With a +2 bonus you have a 20% of chance of moving the effect’s degree of success in your favor, which is huge. This will compete for space with Shield Block, but that only matters if you’re using a shield, which most magi don’t do.

16th Level

Dispelling Spellstrike^SoM: The action economy on this is objectively hard. If you’re not using Starlit Span, you likely need to start your turn in melee with your target and also have Spellstrike charged. Provided you meet those conditions, the counteract effect is on top of your normal Spellstrike, so you’re essentially adding one action to also try to counteract a spell. I’m not sure how you pick which spell to counteract, but that’s a discussion for your GM.
Outside of combat, this is dispel magic for free as often as you want. Is there a spell protecting a door you need to get through? Grab a weapon and hit it until it falls down. The counteract effect is as good as heightening Dispel Magic to the highest level spell you can cast (possibly higher since it can hit 10th level, but the Magus doesn’t get 10th-level spells).
Resounding Cascade^SoM: The damage is decent since by this level your allies will have weapon expertise of some variety, but the 5-foot radius on the aura makes it very difficult to keep allies in the aura.

18th Level

Conflux Wellspring^SoM: Considering that Conflux Spells are among your best choices for recharging Spellstrike, you really want to be able to recharge all of your Focus Points.
Versatile Spellstrike^SoM: The versatility is nice, but not always necessary, and the cost is steep.

20th Level

Supreme Spellstrike^SoM: Solving the need to recharge your Spellstrike leaves that action open for things like moving, which goes a long way to address the Magus’s tightly-constrained action economy.
Whirlwind Spell^SoM: In encounters with multiple enemies, this can be a great way to handle crowds. Of course, you can also cast Fireball, which is considerably easier and less costly than spending your 20th-level feat for a tactic which isn’t always usable.

General Feats

Toughness^CRB: 8+ hit points can be hard for a class that’s almostly exclusively built for melee.

Magus Weapons

The Magus relies heavily on Spellstrike for damage output and for interacting with their class feats. As such, the use of Spellstrike greatly determines both your action economy and your best weapon options. Most importantly: expect to spend most rounds in combat devoting two Actions to a single Spellstrike, and any further attacks are made at the maximum Multiple Attack Penalty, and choose your weaponry around that assumption.

Because making multiple attacks in one turn is such a rarity for the Magus, weapons that make doing so easier or more beneficial are less useful. Weapons with the Agile, Backswing, Forceful, and Swipe properties are less useful than comparable weapons without those traits. Similarly, weapons which need an action to be reloaded will place too much strain on your action economy to justify, so most crossbows and firearms are a poor choice.

Bo Staff^CRB: Tragically, it’s not a “Staff” (which is a specific weapon), so Twisted Tree can’t use this effectively.
Greatsword / Maul^CRB: A good go-to for Inexorable Iron builds if you don’t want Reach. Consider a Maul if you plan to use Shove.
Halberd / Guisarme^CRB: The go-to reach option for Inexorable Iron. Consider a Guisarme instead if you plan to use Trip.
Longbow / Composite Longbow^CRB: Volley is a problem, and the Magus doesn’t get Point-Blank Shot Stance like the Fighter does.
Longsword / Warhammer^CRB: The go-to for Strength-based, one-handed weapon users. Consider a Warhammer if you plan to use Shove.
Rapier^CRB: The go-to for Dexterity-based, one-handed weapon users.
Shortbow / Composite Shortbow^CRB: The go-to option for Starlit Span. Use Composite if you have enough Strength to get bonus damage from Propulsive, but it’s not going to be a ton of damage so don’t stress about it.
Whip^CRB: One-handed, but you still get reach. You’ll need to deal with Nonlethal, but it may be worth the cost for the ability to use Spellstrike from slightly further away.

Magus Armor

Depending on your subclass, you may be able to use light or medium armor effectively, though Starlit Span should stick to light armor and a Dexterity-based build.

Explorer’s Clothing: Once you reach 10th level, your Dexterity could reach 20. At that point, Explorer’s Clothing provides the same AC as Leather Armor, but without a check penalty and with less Bulk. You’ll still want to put runes on it to boost your AC, but transferring runes from your previous armor is easy.
Leather: The go-to starting armor for Dexterity-based builds.
Hide / Scale Mail: 14 Dexterity is a weird choice. You should probably stop at 12 if you’re going to be in medium armor
Chain Mail: Your best medium armor option. Flexible prevents your check penalty from affecting Acrobatics/Athletics checks (not that the Magus makes many of those).

Magus Focus Spells – Conflux Spells

1st-Level Spells

Dimensional Assault^SoM: Massively better than taking a Step, and you get a Strike after casting it.
Force Fang^SoM: Basically Magic Missile as a Focus Spell. Automatic damage is great, and it’s 1 Action that doesn’t care about your Multiple Attack Penalty, so this is a great way to reliably recharge Spellstrike.
Shielding Strike^SoM: Two actions for the price of one.
Shooting Star^SoM: Technically situational, but cover and concealment come up fairly often.
Spinning Staff^SoM: Two Strikes in one Action.
Thunderous Strike^SoM: The damage is pitiful and the cone is small, but it’s 1 Action and also allows you to make a Strike, so the action economy is good, and if you’re lucky you might knock some creatures prone.

3rd-Level Spells

Cascade Countermeasure^SoM: Spellcasters are a small subset of the enemies you’ll face, so this is only situationally useful.

4th-Level Spells

Runic Impression^SoM: Since the Magus relies so heavily on a single big attack from Spellstrike, you’re not making numerous attacks to make the damage from this rune meaningful.
Also: You can add the Returning rune, but the effect ends when you cease to hold the weapon, so if you throw it, the spell ends and the rune goes away. I don’t think that’s the intended behavior, but it appears to be what the rules say.

7th-Level Spells

Hasted Assault^SoM: The Magus’s damage output comes primarily from Spellstrike, which counts as two attacks for the purposes of your Multiple Attack Penalty, which means that you’re likely going to make this Strike at your maximum MAP (-10, or -8 with an Agile weapon). Another action is great, and the action cost here is excellent, but the attack will be consistently unreliable.

Archetypes

Witch / Wizard: Access to more Intelligence-based Arcane spellcasting. This can get you the extra versatility that typical spellcasters enjoy plus additional leveled spells to feed into Spellstrike.

Magus Handbook: PF2 Class Guide – RPGBOT