[Occults] What do you think the powers and weaknesses would be for

Witches could suffer (or profit) from the chance of backfiring spells, angered or benevolent (nature) spirits, being attuned to special altars or monoliths, which allow them to work certain magic - and other not, or the kind of familiar they choose. They might upgrade their magic cauldron one way or the other (maybe using crystals, fossils, metals) which changes the potions they can brew. All those mechanics would have a lot or replayability if done right, and witches could even change "paths" along the way.