Mages that accumulate Power by collecting it via Stones or other stone-based apparatus.
They need to teach stones of their ways to use them, or they can use raw stored power to achieve their goal.
Often associated with the figure of a Taker.
They have their separate list of spells.
PROS:
You can cast as long as you want, if you have stones big enough.
You can have autonomous spells if you teach stones your ways.
You can use other wielder's stones as a source of raw power even if you can't decipher their teachings, and if you can - you just make your ability to cast even stronger.
You can force your will on mind of your enemy or friend.
CONS:
Not enough stones? They are too small? No time to recharge? Too bad!
Good luck teaching stones difficult enough spells for them to be useful.
You need to be in close proximity to your stones, and/or attuned to them.
Forgot what's in the stone and used it as a raw power? Was it your Mnemonia? Good luck restoring that!
Watch you getting robbed for your precious stones. They also did cost you a fortune.