How does spell resistance work?


Advice and Rules Questions


I need clarification of the Spell Resistance rule, pages 564-565 of the Core Rules.

There is an argument about this rule. Some people say:

If I cast Magic Missile on a creature with spell resistance, if I roll under the creature's SR, I can NEVER, EVER, EVER cast Magic Missile on that creature. If I roll over the creature's SR, I can ALWAYS cast Magic Missile on that creature without having to roll for SR.

The problem is, the paragraph in the book is a tad unclear. The paragraph in question reads:

"Check spell resistance only once for any particular casting of a spell or use of a spell-like ability. If spell resistance fails the first time, it fails each time the creature encounters that same casting of the spell. Likewise, if the spell resistance succeeds the first time, it always succeeds. If the creature voluntarily lowered its spell resistance and is then subject to a spell, the creature still has a single chance to resist that spell later, when its spell resistance is back up."

There is more (a whole page) such as spell resistance being like an Armor Class against magic attacks but that paragraph above is the crux.

what I need to know is if the third paragraph is incorrect.


Pathfinder Adventure Path, Rulebook Subscriber

The way I read it, "for any particular casting" and "that same casting" are the key. If you cast the spell SR is checked. If you overcome the SR the creature is affected. If you cast it again then it is a different casting and thus you check SR again. If the spell were one that has an ongoing effect like something that affects an area that the creature moved into then they make the check once and the results are not checked again until that "particular casting of the spell" has ended. So if the SR is not overcome then the creature could go into and out of the area over and over again and be unaffected.

But that is my understanding.


Some effects specify, I believe, that if you fail to overcome SR you cannot use it again on that creature, or not for 24 hours, or some such thing. Unfortunately, I can't come up with specific examples to check actual language off of the top of my head. Maybe someone else can???

In any case, you have to go by the text. Failing special language, it would be what Rhyst said.

For Magic Missile, in particular, one way to look at it is what happens if I target you with 5 missiles from the same spell, when you have SR. I don't get to make a caster check for each missile; either I succeed at the one roll and all 5 missiles hit, or I fail, and all fizzle.


Yeah, lingering and concentration effects are checked for Spell Resistance once, instantaneous spells are checked every time you cast.

If you cast magic missile and it fails, next round you can cast it again with a new SR check. If you cast magic missile and it's successful, next round you can cast it again but it still needs an SR check the second time you cast it.

If you cast telekinetic maneuver, which is a concentration spell, you do ONE SR check, and then the power lasts for 8 rounds (or however many rounds based upon level). If your initial check succeeds, it affects the target for the duration of the spell. Likewise, if you fail, it does not affect that creature for the duration of the spell.

However, if your battle goes long enough to warrant casting a second iteration of Telekinetic Maneuver, you would still do another initial SR check this time as well.

Hope that helps.


Ryze Kuja wrote:

Yeah, lingering and concentration effects are checked for Spell Resistance once, instantaneous spells are checked every time you cast.

If you cast magic missile and it fails, next round you can cast it again with a new SR check. If you cast magic missile and it's successful, next round you can cast it again but it still needs an SR check the second time you cast it.

If you cast telekinetic maneuver, which is a concentration spell, you do ONE SR check, and then the power lasts for 8 rounds (or however many rounds based upon level). If your initial check succeeds, it affects the target for the duration of the spell. Likewise, if you fail, it does not affect that creature for the duration of the spell.

However, if your battle goes long enough to warrant casting a second iteration of Telekinetic Maneuver, you would still do another initial SR check this time as well.

Hope that helps.

So what happens with something like call lighting or aggressive thundercloud which has a repeat roll?


DeathByRugby wrote:
Ryze Kuja wrote:

Yeah, lingering and concentration effects are checked for Spell Resistance once, instantaneous spells are checked every time you cast.

If you cast magic missile and it fails, next round you can cast it again with a new SR check. If you cast magic missile and it's successful, next round you can cast it again but it still needs an SR check the second time you cast it.

If you cast telekinetic maneuver, which is a concentration spell, you do ONE SR check, and then the power lasts for 8 rounds (or however many rounds based upon level). If your initial check succeeds, it affects the target for the duration of the spell. Likewise, if you fail, it does not affect that creature for the duration of the spell.

However, if your battle goes long enough to warrant casting a second iteration of Telekinetic Maneuver, you would still do another initial SR check this time as well.

Hope that helps.

So what happens with something like call lighting or aggressive thundercloud which has a repeat roll?

still only one casting of the spell though. If you cast the spell again, then you could check against SR to see if that casting could work from then on.


DeathByRugby wrote:
So what happens with something like call lighting or aggressive thundercloud which has a repeat roll?

Any time a creature encounters the effects of a specific casting of any spell, the original caster level check applies.

Take the blade barrier spell. Imagine someone cast four copies of that spell in a square. That caster would have to make four caster level checks, one for each side. I wouldn't bother rolling until and unless it matters though.

Then a monster with spell resistance shows up and starts walking through the area. If that monster passes through the "left" blade barrier, the caster makes their roll. If the roll succeeds, the monster is harmed every time they move through that left spell. If the monster then moves through the "right" blade barrier, the caster rolls another caster level check. If that roll fails, the monster can move through that wall unharmed, over and over and over again. But if they go back to the left, that side still always harms them. Same deal with the top and bottom sides... roll their caster level check when required, and it stays the same for that side as long as the duration lasts.

Think of the caster level check as a measure of how well the spell was cast. A caster might barely get it right one casting, but be really, really accurate the next.

That also means that you need to remember what the caster level check was for any ongoing spells, because if a second monster shows up and walks into one of those blade barrier examples, the original rolls still apply.

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