 A coin may make a superior seal because of its iconography; in the Thessalian burial of an initiate described above, for instance, the coin on the lips depicted the apotropaic device of the Gorgon’s head.The seal may also serve to regulate the speech of the dead, which was sometimes sought through rituals for its prophetic powers, but also highly regulated as dangerous; mystery religions that offered arcane knowledge of the afterlife prescribed ritual silence.A golden key "(chrusea klês)" was laid on the tongue of initiates as a symbol of the revelation they were obligated to keep secret.