As with many of the Great Old Ones, Y'golonac's true appearance is unknown, lying sleeping as he does, imprisoned behind a vast wall in an subterranean cavern whose location is unknown. However, when it possesses a mortal creature in order to manifest, it transforms the body to look like a morbidly obese, headless man with a pair of mouths in the palms of its hands.
Whilst many of its kind are unable to comprehend the minds of lesser beings, Y'golonac suffers no such handicap, being capable of conducting perfectly lucid conversations through its host forms. As such, Y'golonac can easily direct his followers, who come from many species and who worship it as a god of perversion and depravity. All of this combines to ensure that it has a vast knowledge of any manner of degenerate practices, not only those which can be conceived of by the human mind.
Summoning The Defiler is possible in a number of ways, such as holding evil thoughts in their minds and thinking of Y'golonac and its proclivities, but the easiest way by far is to simply read or speak its name from the occult text The Revelations of Gla'aki. Once called, it will either offer the summoner a place in its priesthood or simply consume him in an effort to assuage its eternal hunger.
- Cold Print (1987), by Ramsey Campbell.
- Y'golonac (1998), by Daniel Harms.
- Love's Lonely Children (2004), by Richard Watts.