It is a Great Old One whose form is a monstrous hybrid of fibrous, twisted hair-like fungal tendrils and toadstool-like growths which emerges from a mass of bones or a great corpse. Xhamen-Dor has various incarnations and forms it has taken, one of which is that of a serpentine dragon. It originated in Carcosa, from the residue left behind by Hastur which fused with the remnants of the minds and souls of those consumed by Carcosa. Xhamen-Dor borrows into the minds of those who have learned either its name or the true nature of Xhamen-Dor, spreading within their bodies and turning them into undead servants. It has visited countless worlds, turning their inhabitants into the undead, and feeding them to Carcosa.