Demon Form

You gain this spell on a roll of 16 to 66 on the Forbidden Spells List.

Your body transforms into the type of demon whose heart was used as material for the spell.  You gain the stat line, maximum hit points, and abilities of that demon from the manual in which it is found, but you maintain your own consciousness and morality.  At the end of the spell's duration, a moment before you regain your original body, a level 6 fireball centered on you explodes.  You are exempt from this damage.  If you lose your form due to the demon running out of hit points you do not release a fireball on transition.

In addition to the normal Forbidden Spell penalties you must succeed a Wisdom save of DC 8 + the CR of the demon form you took or permanently become Chaotic Evil.