- "We remember those who fell during the Last War. Beware Bertron's curse, for he is named Doomsday."
- ―Translated Kryptonian message[src]
The Last War was a period of warfare that occurred on Krypton at some point long before its destruction, earning its name as the last large-scale conflict before a prolonged era of peace that lasted until the Battle of Krypton.
- "Advising. Action forbidden. It has been decreed by the Council of Krypton that none will ever again give life to a deformity so hateful to sight and memory. The desecration without name."
- ―Service Android[src]
Centuries before its destruction, a brutal war erupted across the planet of Krypton, during which a scientist named Bertron performed a series of genetic experiments which resulted in the creation and release of a deformity with unfathomable power and capacity for destruction. In the aftermath of the war, the creature was destroyed by the Kryptonians and the process of its creation was decreed forbidden by the Council of Krypton.