Xa-Du was a Kryptonian researcher, interested in improving research into suspended animation. However, the unethical nature of his studies led to the Kryptonian Science Council suspending his research and choosing him as the first inmate of the Phantom Zone. A sociopath, Xa-Du swore revenge on the family of the Phantom Zone's discoverer, Jor-El.
Over the course of his incarceration in the Phantom Zone, Xa-Du built an "ecto-suit" to allow him to walk free. However, Krypton exploded before it was complete, and his one attempt at revenge was thwarted by Krypto, the El's dog.
Years later, Xa-Du was able to use the temporarily reactivated Phantom Zone Projector to swap places with Kal-El, son of Jor-El, the hero Superman. Unfortunately his scheme was unsuccessful, and he was banished to the Phantom Zone.
At some point in the future, Xa-Du will become a member of the Anti-Superman Army, a grouping of super-criminals who oppose Superman. They will return through time to fight their enemy; however, they will be stopped.