Spell Resistance

[Merkinsal]

There seem to be several items that increase our characters spell resistance but I can't find an explanation of the math mechanics or a discussion of how much spell resistance is enough. How does spell resistance compare to "protection of the elements" type items? I found a robe of resistance that gives me +17, I had 0 before, and that looked like a high number to me especially since items I have picked up to overcome a mobs spell resistance only give me a +1 or +2 bonus increase, which I assume does not stack but please correct me if I am wrong. Will that +17 protect me most of the time against a bolt of lightning or other elemental type spell and does it work to resist any spell? Final question I promise, do the spell resistance items stack? Any insight is greatly appreciated

[MrCow]

How does spell resistance compare to "protection of the elements" type items?

They don't compare being direct damage spells (fireball, lightning bolt, melf's acid arrow, shout) are not subject to Spell Resistance.

I found a robe of resistance that gives me +17, I had 0 before, and that looked like a high number to me

One of the best analogies to understanding Spell Resistance is to fall back on what you know about AC and To-Hit.

AC/To-hit
When a monster attacks you it uses its to-hit and a 1d20 roll to see if it meets or exceeds your AC. If the number is lower than your AC you dodge/deflect the attack, otherwise, you get hit.

Spell Resistance/Spell Penetration
When a monster casts a spell subject to Spell Resistance it uses its Caster Level (often it is the same as the CR of the monster) and a 1d20 roll to see if it meets or exceeds your SR. If the number is lower than your SR you deflect the spell, otherwise, you get hit with the spell's effect.

do the spell resistance items stack?

Sadly, no.

[Drekisen]

Spell resistance is one of those things like DR, only the highest applies. I have found even with my drow builds, my racial SR does not stack. That being said, spell resistance is about the equivalent of using scrolls that have saves but have no added modifier which makes them signifigantly watered down. SR will help out sometimes, but as you get into higher end content I would be paying a lot more attention to tweaking out your saves and not be so worried about SR. For examlple, so far as I know, about the highest SR u can get at the moment is around 22. Go into an elite quest where the casters are around cr15-18, maybe higher and they are only having to roll between 5-8 to overcome ur SR. That's not really a whole lot, considering they have unlimited mana. Now saves are a different story, and from what I notice, something like my +26 will save on my cleric is going to make me almost immune to stuff like enchantments and necromancy. IMO, pay attention to ur saves, if u can fit it in, keep SR as high as possible for extra cushioning. On a side note, there are some strange creatures that have nasty spells that have resistance checks but ridiculously low cr's....one I can think of, Arcane Skeletons. They have hold person at hard difficulty but so far as I remember they only have a CR5 rating. Of course undead HD is signifigantly higher than thier CR, so thier spell penetration may be also.

[Aesop]

There seem to be several items that increase our characters spell resistance but I can't find an explanation of the math mechanics or a discussion of how much spell resistance is enough.

believe me it is never "enough" the only thing you can do is get as high as you can and hope. The best SR in game comes from the Cleric Spell and since they get a Mass version of it in high caster zones the cleric should throw this up whenever possible (IMO)

Aesop

[Merkinsal]

Thankyou for the feedback. Sounds like a SR is a good thing to have ready and available.