Dug from beneath the Annulii Mountains, this crystal has been shaped by the magical vortex that swathes Ulthuan, so that it draws magical energy towards it.
Once per turn, upon successfully casting a spell, the bearer of the Annulian Crystal can choose to forget that spell and immediately generate another (not including signature spells) in the usual manner.
Note that it is possible the Wizard might generate the spell they just forgot, or one forgotten in a previous turn. Consider it fate.