
And to answer your question, ALL of the above. Any form of magic user whether he use sleight of hand or harnessing infinite cosmic powers.
So illusionists, wizards, sorcerers, witches, warlocks, necromancers, mages, alchemists, bards, scryers, and mindfreaks.
Also, magic worker makes it sounds like they work at a depressing wand factory for minimum mana. Also, they really DO owe their souls to the company store. But hey, that's what you expect when your foreman is Thulsa Doom.