In the DC Universe Imperiex was an evil alien entity, featured in the Our Worlds At War crossover.
He was first mentioned in the Superman titles 2000, when Mongul, the son of the deceased villain of the same name, arrived on Earth saying Imperiex had destroyed Warworld and was heading for Earth. He convinced Superman to help him fight Imperiex. However it transpired that the huge alien entity they had encountered was just a probe; Imperiex Prime himself was a much larger and more powerful being. He had detected imperfections in the fabric of the universe, and his ultimate plan was to destroy it and create a new, perfect one.
President Lex Luthor rallied other superheroes, the military of the U.S. and other countries such as Pokolistan, and several untrustworthy alien allies (including Brainiac-13 and Darkseid) together. They fought the Imperiex probes (and Brainiac's breakaway third faction) until, with the help of the other heroes, Superman managed to send both Imperiex Prime's and Brainiac's conciousness to the Big Bang. Imperiex Prime realised that the imperfection he had detected was himself.
