Mnomquah is a great reptilian creature, with a crown of writhing feelers and empty sockets in place of eyes (though they still work like normal eyes). He is trapped inside the Dreamlands' moon, though how he got trapped there is unknown. He is the mate of the disgusting Oorn, and when the Great Old Ones awaken to lay waste to our world, then Mnomquah will be reunited with his repulsive bride.

He is called the Lord of the Black Lake because he rules over the Lake of Ubboth, a great lake which is under the moon.