Nightmare

 is one of the six core universes in Infinite Crisis.

Earth-43
Tales of horrors prowling the night were once just legends on this Earth - until the darkness returned. Ancient and terrible powers beyond comprehension awoke and brought with them an army of monsters. In fighting these creatures, some heroes have fallen, twisting into monsters themselves. Heroes and villains have set aside old rivalries and are united in fighting darkness that threatens to engulf their world forever.