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 temporary ability damage or permanent ability drain. The ability damage or drain occurs when the spell's duration expires. (There are no corrupt spells with a permanent duration.)
Trin Notes: It is a DM's call, but I would recomend that if a corrupt spell is disrupted during casting or has absolutely no effect for whatever reason (the effect was negated by a successful saving throw, spell resistance, or immunity), then the corruption cost need not be payed. The same could be said about costly spell components and experience point costs as well, with the logic of if a spell did not take effect, then was the energy from the corrupt cost/material component/experience points used? (This did not bother me before noticing a corrupt spell that affects a single target, allows a "Will negates" save and spell resistance, and permanently drains 1 point of wisdom from the caster.)
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 devine spell, and an arcane caster casts it as an arcane spell.
Advanced Spell Components|
In addition to the standard spell components defined in the PLAYER'S HANDBOOK, some of the spells here have the follwing special components.
Corrupt: The caster pays the physical or mental price noted (in temporary ability damage or permanent ability drain) for casting a corrupt spell.
Demon: The caster must be an evil outsider from the Abyss to cast this spell.
Devil: The caster must be an evil outsider from Baator to cast this spell.
Disease: The caster must be infected with the disease named in the spell description to cast this spell.
Drug: The caster must be under the influence of the drug named (see Drugs) in the spell description to cast this spell.
Fiend: The caster must be an outsider from the Lower Planes to cast this spell.
Location: The caster must be standing in a particular place—usually a site dedicated to evil—to cast this spell.
Soul: The caster must have somone's soul, specifically prepared and stored in a proper receptacle (see Souls as Power), to cast this spell.
Undead: The caster must be undead to cast this spell.