Kryptonian trance

A Kryptonian trance is a trance used by Kryptonians to put them into a deep comatose-like state, which makes them appear dead. While under this trance, a Kryptonian can survive the effects of Kryptonite for a much longer time, but only Kryptonian science is able to revive them. On two occasions Superman placed himself in a Kryptonian trance, and everyone believed he was dead. Once in 1985, and then again in 1988. On both occasions it was advanced equipment from the Fortress of Solitude that revived him.