Gothmog is a Great Old One, the son of Shub-Niggurath and the father of the Kellith, also known as Sara Waite, code name Carmilla. His attribute is lust and perversion tempered by love. Unlike other GOOs, he's reasonably well disposed toward Earth and its people, and actively protects it against other GOOs.
Gothmog appears personally in several places in the stories, notably A Simple Game, Insanity Prerequisite and Parents' Day as well as several times during Petra 1: Rock and a Hard Place. When in human form, he tends to use the name Antonio Marques Dominguez.