Cthulhu

Cthulhu was a Great Old One from the Far Realm. Slumbering in the sunken city of R'lyeh somewhere under the Sea of Dragons, Cthulhu was prophesied to awaken when the stars were properly aligned.

Description
Cthulhu's body was of a corpulent, vaguely humanoid shape, covered in rubbery skin, with a head resembling an octopus, its mouth obscured by its mass of tentacles. Upon its back were a pair of powerful wings, like those of a Dragon. Cthulhu was known as the High Priest of the Great Old Ones and was responsible for having led them to the Material Plane from the Far Realm in an age long past. When the stars would properly align, it would be Cthulhu who would awaken and call forth the rest of the Old Ones, bringing them to the material plane for an age of slaughter, revelry, and madness. As an entirely alien being, Cthulhu often incited madness in those who looked upon it, for its form was anathema to the natural life of the world.

History
When the world was still under the control of the Primordials, Cthulhu led a group of Eldritch beings known as the Great Old Ones into the Material Plane, constructing great temple-cities and ruling over their holdings in the chaotic, ever-changing world. Although some among their number were worshiped by the Aboleths, the first race to lay claim to the still-young world, The Old Ones fell into decline, slipping into fitful slumbers, full of Eldritch dreams. It was at this time that their cities sunk, either into the bowels of the earth, or deep beneath the sea, possibly never to be seen again.

In 1452, a group of Cultists, hoping to awaken Cthulhu, began capturing humanoids, including a Verdan named Xendon as sacrifices to the Great Old One. Although he was rescued before he could be sacrificed, Xendon's soul was very nearly claimed by Cthulhu, leaving him with an odd mental link to it, which manifested in Eldritch magic power.