Yasal Crystal
From Shadow of the Throne Wiki
Appearance: Large, yellow crystals of angular facets.
Description: A rare and expensive (R5) crystal, which can imprison small ghosts or spirits who come into contact with it. These spirits are trapped, able only to communicate or transfer use of their powers to the crystal bearer, who in turn has the ability to release them from the stone. Yasal crystals carvved into complex shapes and bound with the correct spirits can sometimes serve as exotic components in artifice.
Yasal crystal is heavily regulated in the Realm, illegal for all but Dragonblooded.