Mantorok is described as the "Corpse God" and the "God of Chaos" and is the only Ancient known to have a physical presence on Earth. Its minions are tinged black and its magick is purple. It is described as the "Keeper of the Ancients" and maintains equilibrium among the other three Ancients. However, due to a powerful binding spell cast by Pious, Mantorok appears to be in a position of inferiority to the other Ancients (it cannot rally its servants and those we do see are weak, skeletal zombies) over the course of the game. Mantorok is a massive, amorphous being with countless eyes and mouths. The murals of its temple depict it as having more defined but still very grotesque shapes, possibly suggesting that Mantorok can change its form at will or that it has merely passed its prime. Its creatures cannot be summoned due to the binding spell cast by Pious. Its magick can restore health, sanity, and magick, and Mantorok-aligned spells have unique abilities.
Compared to the other Ancients, Mantorok is actually much more benevolent towards humanity, once serving as a god of fertility to the ancient Khmer people and setting in motion the 2000 year plan to stop Pious and the Ancient being summoned via giving the Tome Of Eternal Darkness to the chosen few.