- "We remember those who fell during the Last War. Beware Bertron's curse, for he is named Doomsday."
- ―Translated Kryptonian message[src]
At some point in Krypton's history, a great war occurred on the planet. During the conflict, the scientist Bertron performed a genetic experiment which resulted in the creation of a deformity with unfathomable power and capacity for destruction. This deformity was later destroyed.
Ever since Bertron's creation, the Council of Krypton strictly forbade the creation of such a deformity again. However, centuries later, Krypton was destroyed, rendering the Kryptonian species critically endangered. As a result, this law would be ignored by the megalomaniac Lex Luthor, who sought to create another Doomsday as a last ditch attempt in his plans to kill the powerful Kryptonian superhero known by the public as Superman. However, this went awry as Doomsday would have caused the eventual annihilation of humanity had Superman not sacrificed himself to kill Doomsday.