Spell Resistance & Class Levels?

[Ogrork the Mighty]

Does SR go up for creatures when they gain class levels? Or is it HD only?

 

[UltimaGabe]

I believe that it is based on their total Hit Dice, which includes class levels.

 

[Infiniti2000]

For most creatures (all but mind flayer that I can think of actually), there's no rule for increasing SR at all. I suggest you adopt a houserule that works similar to the guideline in the MM, i.e. SR = CR+11. As you advance your monster, increase the SR appropriately per the CR (not per HD).

 

[UltimaGabe]

For most creatures (all but mind flayer that I can think of actually), there's no rule for increasing SR at all.

Drow Traits (Ex): These traits are in addition to the high elf traits, except where noted.
— +2 Intelligence, +2 Charisma.
—Darkvision out to 120 feet. This trait replaces the high elf ’s low-light vision.
—Spell resistance equal to 11 + class levels.
— +2 racial bonus on Will saves against spells and spell-like abilities.
—Spell-Like Abilities: Drow can use the following spell-like abilities once per day: dancing lights, darkness, faerie fire. Caster level equals the drow’s class levels.
—Weapon Proficiency: A drow is automatically proficient with the hand crossbow, the rapier, and the short sword. This trait replaces the high elf ’s weapon proficiency.
—Automatic Languages: Common, Elven, Undercommon. Bonus Languages: Abyssal, Aquan, Draconic, Drow Sign Language, Gnome, Goblin. This trait replaces the high elf ’s automatic and bonus languages.
—Light Blindness: Abrupt exposure to bright light (such as sunlight or a daylight spell) blinds drow for 1 round. On subsequent rounds, they are dazzled as long as they remain in the affected area.
—Favored Class: Wizard (male) or cleric (female). This trait replaces the high elf ’s favored class.
—Level adjustment +2.

Emphasis mine.

 

[dcollins]

I agree that Spell Resistance does not go up or down due to any change in Hit Dice by the RAW. (Drow are a special notable exception.) For example, from the 3rd Ed. FAQ:

Is spell resistance affected by negative levels such as those
from an enervation spell? For example, if I hit a white
dragon with an enervation and bestow 4 negative levels, is
the dragon’s spell resistance now 4 points lower?

No, negative levels don’t affect a creature’s spell resistance;
however, an attacker’s level check to overcome spell resistance
is subject to negative levels. For example, an 18th-level
character with 4 negative level rolls 1d20+14 to make a level
check.

 

[Infiniti2000]

Emphasis mine.

No no, I actually meant drow. Yeah, that's the ticket.