Magic.

What about this, as Rob suggests, 4 kinds of magic: Priest, Ritual, Hermetic and Hedge?

Priest and Hermetic are the most potent. 8 circles in each. Ritual and Hedge are less potent. 5 circles in each. Priest and Ritual are somewhat related, Hermetic and Hedge are somewhat related. Priests are clerics, Hermetics are wizards, Ritualists are witches and voodoo practitioners, Hedge-users are bards and tricksters.

Schools and domains as such:

Priest Domains
Anointment (Blessings)
Conjuration (Summon an avatar)
Damnation (Curses)
Death (Death magic, cause wounds)
Elements (Fire, water, etc…)
Exorcism (Banishment, curse removal)
Life (Healing, curing)
Nature (Plants and animals)
Possession (Charm, geas)
Radiance (Light, warmth)
Revelation (Augury, locate object)
Sanctuary (Protection)

Hermetic Schools
Alteration (Disguise, wish)
Annihilation (Dispel magic, disintegrate)
Astromancy (Astral spells, dimension door)
Charm (Charms)
Creation (Create water, reincarnate)
Divination (Scry, information)
Elemental (Resist fire, waterbreathing)
Enchantment (Enchantments, light)
Evocation (Fireballs, wall of fog)
Horology (Speed, timeportation)
Summoning (Get a xorn)
Wards (Protection, glyphs)

Hedge Schools
Alteration (Disguise)
Charm (Charms)
Divination (Fortune telling, scry)
Illusion (Illusions)
Jinxes (Fumbling, stink, etc…)

Ritual Domains
Anointment (Blessing)
Conjuration (Demon summoning)
Damnation (Curses)
Necromancy (Raise dead)
Voodoo (Eat a heart, feel good)