“Symphony of Destruction”
On Earth -1, Superman had turned evil. The Justice League of that world believed they could save him, but after he killed his Lois Lane, Batman realized he was too far gone. Transforming himself with a Doomsday virus, Batman became the Devastator and killed Superman. Realizing his world was about to die, he is recruited by The Batman Who Laughs to travel to Earth 0 where his mission is to steal cosmic tuning force from the Fortress of Solitude and bring it to Barbatos, who plans to use it to change Earth 0's vibrational frequency to cause it to fall into the Dark Multiverse.