Demogorgon - Prince of Demons
Not much is really known about Demogorgon, other than there has been a recent increase in the number of cultists who worship him that have been found committing atrocities. Some refer to him as Ahmon-Ibor, others Siosicash, but most know him as Demogorgon. He is associated with something referred to as The Gaping Maw, the nature of the association is unclear at best. He is also frequently referenced in conjunction with someone named Malcanthet.
Imagery indicates that he is a massive being with tentacles for arms and two primal ape-like heads, occasionally depicted as having canine heads instead.