Corrupt Magic(Book of Vile Darkness, p. 77—78)
Those who delve into black magic have learned of exceedingly evil spells that, in exchange for foul power, take a terrible toll on the caster. These spells are known as corrupt spells. Their numbers are few, but they are truly horrible applications of magic.
Spellcasters prepare corrupt spells just as they do regular spells, but corrupt spells are available only to spellcasters who prepare spells. Wizards and clerics, for example, can use corrupt magic, but sorcerers and bards cannot. A sorcerer or bard could, however, cast a corrupt spell from a scroll.
A corrupt spell has no material components. Instead, it draws power away from the mental or physical well-being of the caster in the form of ability damage or ability drain. The ability damage or drain occurs when the spell's duration expires. (There are no corrupt spells with a permanent duration.)
If a corrupt spell is made into a potion, scroll, wand, or some other magic item, the user of the item takes the ability damage or ability drain, not the creator. This "corruption cost," mentioned in the spell's descriptive text, is paid each time the item is used.
Corrupt spells are specific to no character class. Furthermore, they aren't inherently divine or arcane spells; a divine caster casting a corrupt spell casts it as a divine spell, and an arcane caster casts it as an arcane spell.