Advancing Spell Resistance

[Three_Haligonians]

Hey there, hoping someone can point me in the right direction on this,

When a creature with spell resistance gets advanced by way of increased HD, does its spell resistance increase in any way? I've looked through the Advancing Monsters chapter of the 3.5 MM and at the Spell Resistance entry in the glosary, but they don't say anything about it.

Where are the rules on it? Are there rules on it?


Thanks

J from Three Haligonians

 

[vexare]

If memory serves me, spell resistance goes up based on CR at the rate of 1/1.

 

[Cheiromancer]

vexare is right, but I don't think it is actually a rule; just a very sensible house rule.

Increasing the caster level of spell like abilities at the same rate (+1 for each +1 CR from hit dice advancement) is also a good rule.

But if you are advancing them by adding class levels,... well, I'd really hesitate before increasing SR or the caster level of SLAs. That would have to be determined on a case by case basis.

 

[Patryn of Elvenshae]

The rule is that SR does not advance unless the creature specifically says it does (like Drow).

 

[wanderer9]

The rule is that SR does not advance unless the creature specifically says it does (like Drow).

And where is this rule located?

 

[Infiniti2000]

It is located in the ethereal plane. Meaning, of course, that it exists because a rule saying that SR increases doesn't exist. If a creature has SR X and nothing says that the SR increases to Y when you add Z HD or Z class levels, then it doesn't. However, as Cheiromancer says, it's a sensible houserule to add +1 SR per increase in CR, though I personally wouldn't increase the SR based on class levels unless the monster description specifically allowed it (like Drow).

 

[Patryn of Elvenshae]

And where is this rule located?

In the section of the Monster Manual dealing with creature advancement. It tells you, there, what changes when something advances.

By extension, anything that it doesn't tell you advances, doesn't.

 

[wanderer9]

It would not be the first time a rule has "missed out" something.

When you think about it, it is strange that some creatures advance their Spell Resistance when they advance by Charcter class, but no creatures advance their Spell Resistance if they advance by HD.

If Spell Resistance is a natural ability that all creatures of that speices have, would not the stronger versions have a greater resistance to spells?

I think it is better to do what is stated above and add SR based on the creatures CR advancement.

Hopefully WoC will add something to their FAQ about this and clarify it in the future.

 

[Patryn of Elvenshae]

It would not be the first time a rule has "missed out" something.

When you think about it, it is strange that some creatures advance their Spell Resistance when they advance by Charcter class, but no creatures advance their Spell Resistance if they advance by HD.

I don't think that it's been missed at all. When SR advances, you are provided with the formula by which it advances. When it doesn't advance, you aren't.

Now, the reason, I assume, that most creatures are not given an adjustable SR is due to the way in which "base" SR is calculated. Generally speaking, a creature has an SR such that a primary caster in a party for which it is designed as a standard encounter (CR = APL) has a ~50% of beating the SR.

When creatures advance, their CR does not always change linearly. For some monsters (like drow), it does. An increase in hit die by one (via a character level) for a drow is equal to an increase in CR by one. The SR advancement formula for drow, then, matches the goal of SR vs. CR.

Other creatures, however, do not follow this path. There is a distinction, for instance, between associated class levels and non-associated class levels: +1 associated = +1 CR, +1 nonassociated = +1/2 CR (until a certain point, when it's +1 CR again). And what's an associated class is most definately a DM call.

Accordingly, there's no easy way to formulaicly tie SR into the generic monster advancement mechanic - except to go in at the end and set it equal to CR + 10 (with the understanding that the advanced CR is a judgement call).