The conflicting stories of the DCU are explained as a Multiverse, containing many parallel universes and alternate versions of the characters, with the primary DC continuity referred to as Earth-One. A cosmic being from the beginning of time known as the Monitor catalogues these realities, but he has an evil counterpart, the Anti-Monitor, who comes from an antimatter universe. After an accident with antimatter on one universe, the Anti-Monitor begins destroying many of the realities with a wave of antimatter, planning on becoming sole ruler of all realities.