Spell Penetration - How/Why

[kotor_fan]

Heya,

After 620 hours, and usually just rolling with it, I have to finally ask:
Why the hell is spell penetration sometimes reduced during calculation?

Example:
I'm currently playing Cruormancer Wizard, spell focus: Necromancy
lvl 12 at the moment, both spell penetration and greater spell penetration selected.
Spell focus and Greater spell focus: Necromancy

Yet sometimes when I cast necromancy spell, it tells me I failed to overcome spell resistance of an enemy. And I'm fine with that, that's what Mythic spell penetration is for.

What I don't understand is this:
My spell penetration according to spellbook: 20

I used boneshatter. Enemy is demodand (from tentacles random encounter).

So why the hell am I seeing "D20 + 8" on attempt to overcome spell resistance?
Why is 20 being reduced to 8 (in my actual example)?

I've seen that happen to my MC on both Wizard and Sorc, on Ember, on Nenio and so on.
Normally I don't care and just let it go, who cares about failed attempt here and there, but now I'm genuinely curious.
Is it some mechanic I'm not seeing, or some formula I'm not getting.
Easier to avoid something happening if I understand why it happens in the first place.

Minor edit: No buffs or debuffs applied other than Holy Symbol of Iomedae (which ironically, should also boost spell pen)

[TamTroll]

i'm sure there's an actual legitimate answer out there somewhere

but after failing the Ivory Sanctum Bridge fight five times in a row due to an un-killable enemy with 40+ Touch AC and good saves across the board...

...i would not be surprised if it was just the game straight up bullshitting you.

[hilburnashua]

There shouldn't be anything in the game that causes you to take a penalty on spell penetration rolls. I would love to see the math on the results of one of these checks to see more what is going on. I would tend to think the game is saying you are getting the spell penetration check (d20) with a bonus of +8 and not showing the +12 for your caster level but I cannot recall ever having seen that before. But I also had to buy a new computer recently and cannot do any testing anymore so nothing I can do the help check this.

Wait, there is one thing that would reduce your spell penetration rolls, negative levels. But if you had 12 negative levels that character would be dead.

[Soul]

think ive heard about this before.... havent verified it in your specific case....

but ive seen people say before and have seen it myself when leveling a character and picking a new spell sometimes there are 2 choices to select from of the same spell.... one is the actual spell and labeled as such and the other is a supernatural ability or something....

think that might be a possible cause.... double check the spell and make sure its labeled as a spell instead of ability....

think the ability version is weaker than the normal spell in that it doesnt factor into your spellbook properly or something because its technically not labeled as a "spell"

and since boneshatter is a 4th level spell.... wizards can get it around level 7 or sorcerers pick up their first level 4 spell at level 8.... so sounds like its treating your caster level as if your just caster level 8 like a sorcerer that just got it....

could also check the damage to see it its nerfed.... just open up your save and target yourself with the spell or a party member who doesnt have spell resistance..... if the spell is treating you as caster level 8 it will be doing 8d6 damage.... otherwise its 1d6 damage per level and caps at 15d6 by 15th level...

[kotor_fan]

Originally posted by Soul:

think ive heard about this before.... havent verified it in your specific case....

but ive seen people say before and have seen it myself when leveling a character and picking a new spell sometimes there are 2 choices to select from of the same spell.... one is the actual spell and labeled as such and the other is a supernatural ability or something....

think that might be a possible cause.... double check the spell and make sure its labeled as a spell instead of ability....

think the ability version is weaker than the normal spell in that it doesnt factor into your spellbook properly or something because its technically not labeled as a "spell"

and since boneshatter is a 4th level spell.... wizards can get it around level 7 or sorcerers pick up their first level 4 spell at level 8.... so sounds like its treating your caster level as if your just caster level 8 like a sorcerer that just got it....

could also check the damage to see it its nerfed.... just open up your save and target yourself with the spell or a party member who doesnt have spell resistance..... if the spell is treating you as caster level 8 it will be doing 8d6 damage.... otherwise its 1d6 damage per level and caps at 15d6 by 15th level...

Nailed it.

Used toybox to search spells list, and yep, there are 2 spells with same name.
Replaced first one with another and didn't see it happen again during testing, spell penetration is calculated properly.
Thank you good sir.