Darkness Points

Darkness points represent the accumulated embodiment of embracing darkness. Too much darkness and a person becomes a creature of darkness forever removed from the light. Furthermore, such creatures usually hate and despise the things they left behind, destroying family, ruining villages, and perverting all that was once sacred and meaningful to them. Each Darkness Point is an effective -1 to Charisma as the internalized darkness subsumes his identity and sense of self. If a character's effective Charisma score ever equals Zero and that character has any darkness points then the character becomes a NPC lich immediately. The NPC has a hatred for all that he once loved. Further darkness points have no impact upon such creatures as they are now creatures of darkness, living (or unliving) embodiments of the power of magic.
Darkness Option: There is one form of magic that is powerful and reliable but mortals are not meant to draw upon it. For the price of one Darkness Point a caster may take 15 on the Shadow Strength check to cast a spell. Only one spell can benefit from this option per darkness point gained; multiple spells can be cast in a single round and multiple spells can be cast as darkness spells in a single round, each generating another point of darkness. This allows reliable access to more powerful spells and effects but the corrupting power of Darkness can quickly control the mightiest of mages, making this an option of desperation or of madness.

One darkness point can be removed by exposure to eight consecutive arcs of direct sunlight. Darkness points are removed one at a time in this fashion. This is the only known way to remove darkness points. Rain, overcast, blizzards, being underground and other effects that prevent direct sunlight from bathing the character prevent the removal of darkness points. Note: if you don't use arcs then use eight hours of sunlight.