Jer-Em was a Kryptonian, an inhabitant of Argo City. When a rocket drive propelled it towards a yellow sun, they gained super powers. Jer-Em believed that the new powers were ungodly, and used his power to push the city back into outer space, causing them to lose their powers. For his crime, he was sentenced to reside in the Phantom Zone for thirty time periods. Soon afterwards, a swarm of meteors pierced the lead shielding of the city, dooming the inhabitants.
Jer-Em feels great remorse for his crime.