Is this possible? The maho-tsukai prestige class from Oriental Adventures (called Tainted Sorcerer in Unearthed Arcana) uses the character's Taint score as its casting stat. 10 + taint determines max spell level, and the taint score itself is added to the save DCs.
Is there any way to do this? Or should I just add a class special describing how it is supposed to work and let the user calculate it?
Is there any way to do this? Or should I just add a class special describing how it is supposed to work and let the user calculate it?