A world at the far reaches of the universe encircled by a giant energy snake called the Oroborus. Sometimes a scale is shed by the giant snake and creatures from earth may enter the planet. This has happened across all time so evolved forms of extinct earth creatures inhabit ranges of Endosrel. The inhabitants range from humanoid animals to mythical animals like dragons, to completely unique species not known to myth or prehistory. Nothing can enter or leave the planet any either way. If anything goes too close to the serpent it consumes it.
Magic exists on Endosrel. It is an energy form created by the planet itself, dragons are it's avatar, and some creatures.
Magic can corrupt creatures and bend them to it's will creating avatars of the various types of magic. One particularly bad case of this is the giant mutant mechanical dragon and crow that terrorize the polluted and vile place place known as The Dark City. Having cleared the flora and fauna of the area and experimenting with dark magic the resident dragon and a simple crow were overcome by the pollution and dark energy and became giant harbingers of doom.