The Unimaginable is an energy being who traveled to Earth after studying it from afar. He was especially taken with the exploits of the Justice League of America, and resolved to become one of their number. Finding out that Metamorpho is going to be offered a spot, the Unimaginable tries defeat him in combat to prove his worth. The JLA arrive and end up defeating the energy being.
Some time later, on Starlag II, The Unimaginable returned and took the control of an alien named Dr Bendorian, using him to escape and wreak havoc on the prison.
More recently, Lex Luthor succeeded of opening the chamber and utilized all the power in Maximum, trying to control him. Fortunately, Maximum was brought back to reason by his friend, the other members of the Supermen of America. He finally scatters the entire divine power all around the world, apparently destroying the being named The Unimaginable.
The New 52
The Unimaginable comes into conflict with the new Justice League Unlimited.
Powers and Abilities
The Unimaginable is able to control any inorganic matter. Fueled by causing stars to supernova, The Unimaginable is vastly powerful.