Drawing on the powers of Darkness
This allows an ensouled being to draw upon the powers of Darkness (aka Evil, sorta) for temporary powers. The knowledge to do this is restricted and Good agents attempt to suppress it, but it is reseeded by the lower powers. Each character who draws upon this power knows the source they are drawing from and may only do so of their own free will, accepting the penalties for doing so.
Each use allows a +4 to ANY roll, a spell to be used as if it was one level lower for a single casting. Each use gives the character 1d4 Corruption points. When a being has a number of points equal to their nonmagical Will Save they roll a Will save at a GMO DC that is scaled to level and the purpose/intent of the power and reset their score to 0. If the save is failed, the character falls by 1 step as indicated below.
Corruption naturally decreases at a rate of 1 per week or month (GMO). This can be increased if penance is performed or if the being makes genuine acts of dedication and sacrifice to balance the karmic scales. While this Corruption will fade a character is still using Evil and performing acts of Evil in using this power, this will over time shift a character’s alignment to Evil.
0 Dabbler inobvious to normal sight, but user shows up on various occult senses as a dark magic user.
1-2 Temptation A visible brand is now on the characters body, this brand becomes increasingly difficult to hide.
3-4 Pact The being has a formal pact with a specific lower power (this can be a specific one if the character attempts to choose, or whichever power was first to grant the boon. This pact is roughly on par with having a temporary Devil’s Mark pact.
5-6 Transformation The body of the being is becoming warped and twisted to reflect the corruption the user draws upon, they are likely hunted and now are so in debt to their patron that they must perform many tasks for them or face punishment.
7 Agency The being is almost entirely corrupted and certainly ranks among the damned and is likely possessed, though the possessing spirit is a rider with no intrinsic period of dominance.
8 Possession The being is now host to a dominant possessing power and rarely has any periods of dominance.