Tsathoggua (the Sleeper of N’kai) is an amorphous, toad-like god-creature mentioned in the Pnakotic Manuscripts and the Necronomicon and the Commoriom myth-cycle preserved by the Atlantean high-priest Klarkash-Ton.
His most common form is very squat and pot-bellied, his head like a monstrous toad and his whole body covered with an imitation of short fur, giving somehow a vague sensation of both the bat and the sloth. His sleepy lids usually half-lowered over his globular eyes, giving him the look of a sleepy black toad which he has eternally. He will rise not from his place, even in the ravening of hunger, but will wait in divine slothfulness for the sacrifice.
Tsathoggua abides deep inside the earth, in black, lightless N’kai. He once dwelt inside Mount Voormithadreth in Hyberborea, but left after the continent iced over.
Tsathoggua is served by his formless spawn, polymorphic entities made of black protoplasm. They are extremely resilient and very difficult to dispatch. Formless spawn can take any shape and can attack their targets in nearly every conceivable way. They are surprisingly flexible and plastic-like, and can quickly flow into a room through the tiniest of cracks. They attack by trampling their targets, biting them, or crushing them with their grasp. Formless spawn often rest in basins in Tsathoggua’s temples and keep the sanctuary from being defiled by nonbelievers.
A few daring mystics have hinted at a pre-Pleistocene origin for the fragmentary Pnakotic Manuscripts, and have suggested that the devotees of Tsathoggua were as alien to mankind as Tsathoggua itself.