amusingly, in the time between replies the setting has evolved a little.
Instead of pacts we now have Grafts, parts of demons that you force to fuse with your own body to gain power. We also have 6 different flavors of spellcaster, split between angelic and demonic power sources.
Angelic:
~Fundamentalist (Earth, Wind, Water)
~Genesis Caller (Summoning)
~Lux Weaver (Light)
Demonic:
~Arcanist (Fire, Lightning, Ice)
~Umbra Weaver (Darkness)
~Dreamwalker (Dreams)
All with basic attacks, of course, but flavored very differnently. An Arcanist might set you on fire, but a Genesis Caller will summon a swarm of angelic butterflies to peel off your flesh.
Plus some friends of mine have been helping me with magic items for the setting, my favorite being Charon's Obol. It brings whoever holds it back from death once, as they use it to pay their way back up the river styx into their body, but when they die again they can't go to the afterlife at all, becoming an eternally tormented spirit wandering the earth until someone somehow destroys them.
Stuff like that is the general vibe I'm going for, a setting where all the sharpest swords are double edged.