[PFKM] Do spellcasters need spell penetration?

[Trashos]

There are 4 feats that raise a spellcaster's penetration. They are the following feats:
- Spell Penetration (+2 to spell penetration),
- Greater Spell Penetration (another +2 to spell penetration),
- Allied Spellcaster (TW feat) (another +2 to spell penetration if adjacent to ally who also has the feat), and
- Spell Specialization (raises your spellcaster level by 2 for the chosen spell, so effectively it raises your spell penetration +2 for this spell).

Spell Specialization has other important features too, so here I am mainly going to help you answer the question: Do I need the feats Spell Penetration, Greater Spell Penetration and Allied Spellcaster?


Notes:

Spoiler

Note#1: I may have missed some enemies. If I have missed someone important, please let me know.
Note#2: I have not looked into the dlc enemies.
Note#3: Not all spell are hindered by enemy SR. For example, Chains of Light doesn't get affected. But most spells do.
Note#4: Some enemies have spell immunities. That's a different mechanic, and we are not going to discuss it here.
Note#5: Elves come with an inherent +2 to spell penetration.

Note#6:
This work is not very original. All I did was go through the list of Kingmaker combatants and note down the Spell Resistance (SR) of the enemies. The list of combatants is here:
https://pathfinderkingmaker.gamepedia.com/Category:Combatants
I have done this for my own use. But since I did it, I thought I might as well let you know of the results.

Theory:

Spoiler

When the enemy has no spell resistance, you do not need spell penetration.
When the enemy has spell resistance X, you roll d20 and your final spell penetration is given by the formula:

1d20+ spellcaster level + bonuses

If your final penetration does not at least match the enemy's Spell Resistance, then your spell does not go through. Therefore, if an enemy has SR20 and you are lvl10 with no feats related to penetration, you need to roll a 10 to penetrate. If you also have the feats Spell Penetration (+2 bonus) and Greater Spell Penetration (+2 bonus), you only need to roll a 6 to penetrate.

If you penetrate, the enemy rolls against your spell's DC with his related saving throw in order to save. This result depends on a different formula, and the helpful feats for this are Spell Focus and Greater Spell Focus. If you don't penetrate, nothing happens.

List of enemies with SR:

Spoiler

I have not listed dlc enemies.
I have not listed enemies with SR0, which is most enemies.
Note that some enemies have nonzero but low SR, and therefore it is trivial to bypass their SR without any feats, if you meet them at a high enough level.

SR 33 Lady Primrose
SR 32 Ilthuliak, Knurly Witch
SR 31 Jabberwock
SR 30 Ferocious Devourer
SR 29 Patient Shadow
SR 27 Astradaemon, Vilderavn
SR 25 Erinyes, Lady of Shallows
SR 24 Quickwood
SR 23 Dweomerlion
SR 22 Black/Purple Dweomerowlbear
SR 21 Nereid, Bogeyman
SR 20 Dweomercat, Nixie Trickster
SR 19 Ankou
SR 18 Ancient Soul Eater, Doomspider, Purple Worm, Greater Dweomanticore
SR 17 Ancient Elementals
SR 16 Elder Elementals
SR 15 Great Nightmare, Nixie Prankster
SR 14 Ferocious Soul Eater, Greater Elementals
SR 12 Huge Elementals, Soul Eater
SR 11 Siroket
SR 10 Large Elementals
SR 08 Hellhound, Medium Elementals
SR 06 Small Elementals
SR 05 Guardian Armor
SR 00 Most Enemies

Conclusion:
Most enemies do not have spell resistance. Many bosses and mini bosses do not have spell resistance. The list of spell resistances above shows which enemies have SR. Unless your tactics absolutely depend on hitting with spells in all scenarios, I would say that spell penetration is not very important, and you can make do with bombs against those enemies who have high SR. At any rate, in my opinion, taking Spell Penetration is OK but not a high priority, Greater Spell Penetration is pushing it, and in all probability you have many better options than Allied Spellcaster.

 

[Desiderius]

Single target non burn?

Yes

Otherwise no

Elves come with +2

 

[Xamenos]

So, what feats are you taking instead of the two Penetrations? Cause analyzing in a vacuum is well and good, but you have to consider the number of better feat options for pure casters and the number of feats they get.

 

[Trashos]

Xamenos, You can focus on an additional school instead to raise your DC for that school or take the metamagic feats. But if you have nothing else helpful to take, then by all means take the Penetration feats. They are going to help against the few enemies with significant SR.

Battlemages like Eldritch Knights are better off taking fighter feats instead, even if they are planning to do significant spellcasting.

Elves come with +2

Forgot about that, gonna add it in OP. Thanks!

 

[Desiderius]

Xamenos, You can focus on an additional school instead to raise your DC for that school or take the metamagic feats. But if you have nothing else helpful to take, then by all means take the Penetration feats. They are going to help against the few enemies with significant SR.

Battlemages like Eldritch Knights are better off taking fighter feats instead, even if they are planning to do significant spellcasting.

Elves come with +2

Forgot about that, gonna add it in OP. Thanks!

All comes down to action economy.

 

[Xamenos]

Xamenos, You can focus on an additional school instead to raise your DC for that school or take the metamagic feats. But if you have nothing else helpful to take, then by all means take the Penetration feats. They are going to help against the few enemies with significant SR.

Battlemages like Eldritch Knights are better off taking fighter feats instead, even if they are planning to do significant spellcasting.

Elves come with +2

Forgot about that, gonna add it in OP. Thanks!

Alright then, let's talk specifics. Let's assume we want to build a generic (ie not a ray spammer) wizard. He gets 10 feats, +5 because he's a wizard, +1 if he's a human. Focusing on two schools requires 4 feats. If one of those is Evocation, we can add two Elemental Focuses for a total of 6. If you want to be a summoner we can add Augment Summoning and Superior Summoning. You can't really Focus on too much, or you quickly run out of slots and actions. So I feel confident in saying 8 feats is the absolute maximum required for your schools. Improved Initiative, Combat Casting and Spell Specialization range from mandatory to useful for everyone, and they bring us to 11. Metamagic Feats are good, but again you can't take too many of them and they only start proving their worth at higher levels. The only ones I consider essential are Quicken, which lets you trade slots for actions, and Heighten, which can't be duplicated by a Rod. That makes 13. Two short of the 15 that any Wizard gets. So any Wizard can get both Penetrations without missing out on anything, though I certainly agree Allied Spellcaster is superfluous. A Human can also get Empower or Extend with his extra feat. Or any other race could swap Combat Casting for one of those Metamagics. And someone who does not Focus on both Evocation and Conjuration will have even more space to fill.

Next, let's say you prefer a Ray spammer. If you want her to become an Arcane Trickster (and you should), you'll only get 2 of the bonus wizard feats, for a total of 13 or 14. You will want Accomplished Sneak Attacker - Point Blank Shot - Precise Shot - Weapon Focus - Improved Critical, two Evocation and two Elemental Focuses. Improved Initiative and Spell Specialization are even more mandatory here, and I wouldn't recommend skipping on Quicken and Empower, though Heighten and Extend are not really useful for such a Wizard. And that's all the available feats. (Humans get 1 extra, but Octavia has it filled with Transmutation Focus) So getting Spell Penetration is a legitimate choice with drawbacks here. Personally, I'd take them both instead of the Elemental Focuses because I really, really don't want my major ranged damage dealer to whiff on those fights.

Now, I've gotten bored so I'm just gonna speed through the rest:

An Alchemist should never take Spell Penetration. Bombs are unaffected by Spell Resistance, and he has no business casting other offensive spells.

A Bard should always take Spell Penetration. She's always focusing on Enchantment and doesn't have need for more feats.

A Cleric doesn't need a second Focus, so he should take Spell Penetration to make sure his spells connect if he plans to be casting offensive spells at all.

There are two kinds of fighter/mages: The kind that buffs themselves and hit with a sword don't want Penetration at all. But it's useful for the kind that attacks with touch spells (Magus) and with their bonus feats and not needing a Focus they can probably take it without sacrificing anything important.

 

[Desiderius]

Anyone near melee wants Shake it Off and Blindfight. Bards can focus on either Enchantment, Evocation (Sonic) and/or attacking/Dazzling action economy. Probably better off focusing on AoE effects on higher difficulties so can skip Spell Pen until later or forgo altogether. R4/AT doesn't need it because can just use weapons.

Tristian doesn't need it because he has AoE Fire and can bypass with Chains of Light. Necro Harrim could take it for Boneshatters and Destructions and the like but may not need it.

End of the day probably better off just ganking bosses that have high SR but might as well get it on pure casters because otherwise you're picking your butt on fights where you're supposed to be the most important.

 

[Xamenos]

Alright, I oversimplified a bit for some cases. I remain unconvinced that Blindfight is essential when its major advantage, the immunity to gaze attacks, can largely be replicated by spells and consumables by the time you need it but I won't argue it's a nice-to-have. AoE spells are still affected by Spell Resistance, so you want Penetration for them too. And what are you doing as an Arcane Trickster if you don't plan to blast fools with spells?

 

[Mr. Magniloquent]

Spell penetration typically isn't necessary. While saving throws are very bloated in PF:KM, spell resistances aren't really impacted, as they are not influenced by attributes. Your own spellcasting modifiers should be high enough to overcome spell resistance without issue. I think I have exactly one memory of that occurring on my Arcane Trickster--but he was also an elf. I prefer to just get Spell Focuses, but I prefer generalist wizards typically.

Not a bad analysis by Xamenos, but I can't agree with all of it.

Metamagic feats have limited value in PF:KM, largely because of the availability of rods. Extend is cheap and available, with empower rods not being far behind. They will serve your purposes for all but the most gimmicky and one-trick builds. Normally, these are the two best metamagic feats, but rods really steal their thunder. They're superior to the metamagic feats, as you can still use the lower level spell slot. They will only start to become attractive very late game. Quicken is an awful choice unless you have something very specific in mind, such as an alpha strike for a special encounter or saving an emergency Break Enchantment/Dispel in reserve. Neither are particularly necessary in KM. Maximize is too expensive. Empower has more utility and averages out to being as good (if not better) at a better cost. The only metamagic feat in KM that's truly worth it is Heighten Spell. By nature of specialization and not all spells being equal, this feat allows you to keep your spell book full of what works.

Combat Casting is an awful feat unless you're a Gish. Touch spells are prominent enough to where paying the Point Blank Shot tax to get to Precise Shot, and even Improved Precise Shot are merited. Concealment is common on enemies, particularly the ones that matter. Blind Fight isn't necessary on a pure caster, but can be really useful as there are many scenarios were concealed enemies will spawn from behind. I can't support Weapon Focus - Ray or Improved Critical - Ray, even on an Arcane Trickster. Two feats for +1 BAB and +5% chance to critical is not a good deal for spell casting. Elemental Focus is OK for Clerics and Arcane Tricksters, but it is outstanding for Sorcerers--particularly elemental bloodlines. Improved Initiative is imperative for all spell casters, always. Spell Specialization is a pretty good choice, since you will inevitably begin to favor certain spells. I wouldn't take it more than 2 or 3 times though. I like "Shake It Off" on everyone, as it's a very cost effective way to majorly improve all of your saves.

 

[Desiderius]

Trash listed the mobs where SR is very much an issue. If it isn’t for you try upping the difficulty. In any case early on you don’t have the levels to get close so take other things but once you get some spell pen items and what not each feat reduces you chances of whiffing by 25-50% so worth it then.

Mostly optional but if you’re not fighting those what are you even doing. Not really needed for AoE because the mobs you’re worried about are bosses.

 

[Desiderius]

Shake it Off is poor on ranged toons because they’re not close to the rest of your team. AT uses Rays when they need to target touch or want the effect or can bypass resistance and weapons vs randoms and mobs with high SR if you can get them flat-footed.

Kind of a choice between Spell Pen and Shatter and certainly on WotR I’ll be going all in on Shatter vs Demons who are very susceptible to Fear. If they weren’t they wouldn’t be Demons. In P:K you had a lot of Undead (Ghosts especially) and mindless Vermin.

 

[Trashos]

Note the SR list. The SR of Ankou, Purple Worm, Hellhounds, Siroket, Guardian Armor is irrelevant, because at the point you meet them you are high enough level to penetrate just because of your level. I will also argue that spells should not be used against Dweomercats, because they immediately go after the mage if a spell is cast on them, and you 'd rather they stuck to your tanks.

So the list of enemies with significant SR is basically Knurly Witch, Ilthuliak, the Ferocious Devourers , the Jabberwack, several fey (Lady Primrose, Lady of Shallows, Nixies, Nereids), some Dweomeranimals, the Elementals, the high level Soul Eaters, Astradaemon, Patient Shadow, Erinyes, Doomspider, Quickwood, Greater Nightmare, Boogeymen, and Vilderavn. Those are all the enemies where penetration feats will help. Obviously there is some of them, but they are not that many.

Another important argument is that certain few attacking spells are not affected by SR. Notably, Chains of Light (which can help your physical weapon attackers greatly), and some acid spells. These are great options against enemies with high SR (not to mention bombs).

I wanted to write this down for future reference, and I am soon returning to answer the specific points that have been brought up.

 

[Mr. Magniloquent]

Most of those enemies aren't going to be fought until you CL is 2/3 to 3/4 of their SR anyway. Getting Spell Penetration helps, but it's not a priority. The enemies were SR is truly is a liability are likely to have saves and immunities were taking them down directly with spells isn't a good first choice. Spells which stand a good chance impose conditions which require repeat checks anyway. I still take it, but that as much to do with a general "meh" selection of spell casting feats as anything else.

I still like Shake it Off on everyone though. At worst it typically ends up granting a +2, which is still great. Even on most exterior ground maps, most of my party is in proximity to enjoy the benefits. On any interior or subterranean maps, it's practically assured.

 

[Desiderius]

No Trash you’re theorycrafting again. Those are DLC mobs where you’re not very high level at all so you really do need it.

The point where you’re getting closer from CL is where the feat is most valuable, reducing miss chance up to 100% when your native SP = SR - 2

 

[Desiderius]

So you’re an Elf Wiz18 vs Ithulliak (SR 32) with 6 SP from items.

SP feats reduce miss chance from 2/5 to 1/5 = 50% reduction.

Sry Elf Wiz is 2/3 reduction (3/10->1/10)

 

[Xamenos]

So you’re an Elf Wiz18 vs Ithulliak (SR 32) with 6 SP from items.

SP feats reduce miss chance from 2/5 to 1/5 = 50% reduction.

Sry Elf Wiz is 2/3 reduction (3/10->1/10)

This is exactly the piece of math that everyone gets wrong about Armor Class and Attack Bonuses. The more of both you have, the more benefit you get from each additional point. Until, of course, you hit the limit.

 

[Cleric of Asmodeus]

Interesting discussion.

Case study: My current level 14 Wiz/AT

Feats
Spell Focus (Evocation)
Greater Spell Focus (Evocation)
Point Blank Shot
Precise Shot
Accomplished Sneak Attacker
Spell Penetration
Greater Spell Penetration
Weapon Focus (Ray)

AT: Sneak attack AoE (yes!), Improved Invis, Impromptu Sneak Attack

Relevant Items:
Rod of Flaming Vengeance (all spells are fire, CL+1, DC+3 Evocation)
Amulet of Four Elements (+1 damage per die)
Robe of True Master (+4 Spell Pen)
+6 Enhancement Int Head Thingy
+4 Profane Int Staff
Crimson Counselor (3x Scorching ray or 2x Fireball)
2 Lesser Quicken Rods
2 Lesser Maximize Rods

Dex 22, Int 33

I actually have a grandmaster's rod (ignore spell resistance) and burning amulet (+4 CL for some select fire spells) but they are on my Ecclessitheurge. She has Weather as primary domain so she has been memorizing 4 Fire Storms in the level 7 slot and I don't have any of the spell pen feats on her.

I have 4 more feats until maxing out at 19th. Options are: Improved Crit (Ray), Spell Specialization (Hellfire Ray), Dazzle/Shatter, Elemental Focus (Fire), Spell Focus (Conjuration? Transmutation?), Blind Fight, Shake it Off, Skill Focus (Perception), Heighten Spell, Empower Spell, other Skill Focus

Spell slots:

1st
Magic Missile x 5, Mage Armor for a pet, Shield, Expeditious Retreat
Magic Missile has no save, no attack rolle

2nd
Scorching Ray x 4, Sense Vitals, Mirror Image, Stone Rain*
Scorching Ray has no save but has attack roll
Stone Rain has no spell resistance, save, or attack roll
Sense Vitals is an opposition school

3rd
Battering Blast x 4, Fireball x 3, Resist Energy Communal

4th
Controlled Fireball x 3, Dragon's Breath, Volcanic Storm**, False Life (Greater), Protection from Energy (Communal)
Dragon's Breath has no spell resistance.

5th
Icy Prison, Acidic Spray, Phantasmal Web x 3, Animal Growth
Phantasmal Web is one of my few options for high AC/Evasive targets since it doesn't target Reflex.

6th
Chain Lightning x 4, Mass Owl

Mass Owl is pretty lazy, mostly to give me a party-wide boost on perception rolls. I will get Hellfire Ray when I hit 15th and frankly am probably missing some really big numbers from this without Spell Specialization and grandmaster's rod. Cleric has Sirocco and also I hate it. Cold Ice Strike has sweet action economy but I can't always get the line of sight and the quicken rods pull a lot of duty here; cleric uses it.

7th
Prismatic Spray, Legendary Proportions * 3

Kind of a bunk spell level so far but maybe it's the scrolls I have found. But I don't have another Legendary Proporter yet so this is absolutely fine.

* Stone rain: we get mass featherstep elsewhere and it's occasionally handy to start an encounter with difficult terrain and the sneak attack damage, mostly for endurance runs when I'm low on spells and want to avoid taking hits. It also doesn't have any saves or resistance and so if the encounter is vulnerable to difficult terrain, it's sneaky good.
** Same deal with Volcanic Storm, and i get to apply sneak attack twice because Owlcat

High target encounter:
Maximized Chain Lightning and Quickened Fireball (Cleric casts maximized Firestorm)
Phantasmal Web (Bard has this too)

Fewer, more urgent targets:
Maximized/Quickened Blasts+Rays, Sense Vitals

High Saves:
Rays, Volcanic Storm, Magic Missile

High Spell Resistance:
Storm, Rain, Dragon's Breath

Evasive:
Phantasmal Web, Rays, Rain/Storm

Fire Immune
Oops. Savor the challenge and probably use energy resist (Fire). Phantasmal Web and Prismatic Spray.

Replacement level feats: I've considered Blind Fighting and Skill Focus (Blah) as replacement level feats, as sort of the floor of how good a feat needs to be to be worth taking at all. Sounds like I should add Shake it Off to that list; I hadn't really considered it closely before. I have a pounce barb and a lot of ranged attacks so we tend to be in a 30ft blob these days in a lot of encounters.

 

[Cleric of Asmodeus]

After writing all of this, thinking that Empower Spell would be a good option to use with the Fiery Vengeance, and I probably should give the grand master's rod and hellfire ray a spin soon.

 

[Trashos]

Xamenos,

Note that I am not saying that Spell Penetration feats are completely useless. I worded the thread title as a question, and I specifically explained in OP that my goal is to help you answer the question for yourselves. I did give my own opinion too (in which I mentioned that taking the first Spell Penetration looks OK to me, although I do not consider it a high priority), which is what we are debating.

Your main argument seems to be "What are Spell Penetration feats competing with?". Indeed, this is the best way to think about it. Once a Wizard is done with his School Focus feats, a couple of other feats that his plan may require, and his choice of metamagic feats (we all seem to agree at least on Heighten), then Spell Penetration feats are fair game.

Personally, I 'd certainly take Shake it Off, Blindfight, and arguably feats that improve saving throws and Persuasion over Spell Penetration or at least the Greater version (not to mention Allied Spellcaster, but we seem to agree on this). You wouldn't, and that's fine.

PS. Shake it Off is freaking awesome, and I unite my voice with everyone who mentioned it here.

 

[Yosharian]

Alright, I oversimplified a bit for some cases. I remain unconvinced that Blindfight is essential when its major advantage, the immunity to gaze attacks, can largely be replicated by spells and consumables by the time you need it but I won't argue it's a nice-to-have. AoE spells are still affected by Spell Resistance, so you want Penetration for them too. And what are you doing as an Arcane Trickster if you don't plan to blast fools with spells?

This is all very well but Wild Hunt are very capable of Dispelling so all those protections can easily get dropped

 

[Trashos]

No Trash you’re theorycrafting again. Those are DLC mobs where you’re not very high level at all so you really do need it.

I do not have the dlc. Which of the SR enemies are met in dlc in lower level than in the base game?

 

[deuxhero]

Read the spell descriptions. Plenty of spells don't even require SR rolls. Spells that impact the terrain are a big one and absolutely shut down many bosses with SR, and often just destroy magic immune (infinite SR) monsters. Grease comes to mind since golems and big enemies tend to have terrible reflex saves.

 

[Trashos]

This is exactly the piece of math that everyone gets wrong about Armor Class and Attack Bonuses. The more of both you have, the more benefit you get from each additional point. Until, of course, you hit the limit.

I agree, although I want to make a distinction between magic and physical attacks. With magic, you are not going to get 30 spells off during the fight. So unless you are absolutely certain that everything will hit within a couple of tries, you need a backup plan. And if you have a backup plan in place (which you should), then losing some statistical probability with your spells is not a big deal anymore.

 

[LannTheStupid]

I think it is more or less obvious that Spell Penetration is not necessary for DC control wizards, but obligatory for nukers like Arcane Trickster. Which goes for the whole concept of "Pathfinder wizards do not do direct damage".

 

[Trashos]

RE: Blindfight

I always take it on everyone. It is extremely useful against the Wild Hunt and Medusas. I think it also works against the Defaced Sisters, but tbh I will have to check this again in practice.

Note that in Ch7 you are constantly completely surrounded by Wild Hunt who are gazing from all sides. It is an optional chapter of course, and you may or may not be interested in it. Similar situations can arise in Ch 6, depending on your approach to getting through HATEOT. If you go guns blazing, you are bound to need Blindfight there too.

You guys who don't use Blindfight, what buffs are you using that provide the same effect?