Long ago in ancient times, R'lyeh was an evil god large enough to cover the entire sea floor. Over the course of hundreds of millions of years, it gave birth to many other evil gods before falling into a deep slumber. It wasn't until darkness covered the world and there was a necessity for him to again cover the world in evil that he awoke...
R'lyeh is the name of Cthulhu's lost city at the bottom of the Pacific Ocean. H.P. Lovecraft first introduced this city as part of his Cthulhu Mythos in 1928 with the short story "The Call of Cthulhu". As a city, it is characterized by its bizarre, non-Euclidian geometry - appropriate, considering its purpose as an abode for the Great Old Ones.