Spider Mastermind

The Spider Mastermind (also known as the Spidermind or Spiderdemon) was a leader of the forces of Hell. The Spider Mastermind is a Spiderdemon, appearing as an immense exposed brain, with two useless arms and relatively humanoid facial features. Incapable of movement on its own, it is grafted to a four-legged chassis that provides movement and possibly life support. The Spider Mastermind is armed with a "Super Chaingun" that launches explosive rounds. The Spider Mastermind, alongside the Cyberdemon, lead an invasion of Hell's forces to dominate the UAC facilities on the twin moons of Mars; Phobos and Deimos.

The Spider Mastermind resided in the city of Dis, and was killed by a lone UAC Marine. While more members of its species have been shown in action, it is possible that, after this event, the Icon of Sin decided to demote the Spiderdemons to a similar level of a Cyberdemon. While the original Spider Mastermind was killed in 2022, another Spiderdemon took on its title and rose to the rank of Dark Lord by 2149, and other Spiderdemons have also been referred to with the title of Spider Mastermind.