Earth-15 was a place unlike any other. A near-utopia, this world was free of the problems and issues that plagued the other worlds of the Multiverse.
In the prime of their lives and at the height of their powers, Earth-15’s highly evolved heroes preserved order and peace for those living there. With crime virtually wiped out, Earth-15’s citizens relished in the comfort and security of knowing their perfect lives on this perfect planet were free from strife. This was a place where certainly nothing could go wrong—where each day was more wonderful than the last.
Then it happened…
Without warning, the being known as Superboy-Prime came to shatter the serene bubble Earth-15 had been living in. Its peaceful heroes stood little chance against the unimaginable strength and malice he brought. Making quick work of its protectors, Superboy-Prime turned his immense rage towards its citizens—wiping out billions of lives before completely destroying the planet itself.
The only remnant of this once-perfect universe is a vastly powerful fragment known as the Cosmic Grail. Its exact whereabouts are unknown, as it remains hidden somewhere among the many worlds of the Multiverse.
JUSTICE LEAGUE OF AMERICA #15 (1962)