The Gods of Revenge, led by A'Bhaath, created the Abyss in the shadows of the Dome of Heavens, a place of eternal darkness and shadow, that provides the Dome of Heaven its foundations. Without one, the other could not exist.
The Abyss. a vast plane of emptiness, was made home the Revengers. It is said that whatever one imagines is possible, through it is always horribly twisted in some fashion. The Gods of Revenge Have secret lairs in this realms, though the deity's Ghao Dhu Bronze Tower is said to stand starkly at the edge of the Abyss.