Caster level

From NWNWiki

The caster level of a cast spell is a measure of the power of that particular casting. For spells cast from items, this number is given in parentheses after the relevant item property. For spells cast by a character, the caster level is the character's level in the class used to cast the spell. (Epic spells cast from items are an exception in that their caster level is not given in parentheses. The caster level for most default epic spell item properties is 25, with the exceptions being epic warding and hellball, for which the caster level is 30.)

Level drain effects can cause a character's caster level to decrease, affecting spell duration and damage.

Note: A common misconception is that pale master levels add to caster level. They do not.

[edit] Special abilities

Special abilities can also have caster levels associated with them. For player characters, these special abilities usually come in the form of feats associated with a particular class; the caster level of these special abilities is the associated class level. (This is not affected by level drain.) For monsters, special abilities are usually assigned in the Toolset; at the same time, each such ability is assigned a fixed caster level (possibly unrelated to any class level).