Spiderdemon

The Spiderdemon (also known as the Spider Mastermind, as named in The Ultimate Doom, Doom II, Final Doom and the Depths of Doom Trilogy's manual) is the final boss of the first Doom, and appears again in the final episode of The Ultimate Doom, Thy Flesh Consumed. The PlayStation and Saturn versions of Doom in turn feature two Spiderdemons as the bosses of its final level, Redemption Denied on harder skill levels. The Spiderdemon has 3000 hit points and is one of the toughest creatures in the game.

Background
Spider Masterminds can be both male or female... But its not clear how one checks its gender...

The Doom II game booklet presents the Spiderdemon as the mother of the Arachnotrons: "You guess the Arachnotrons had to come from somewhere. Hi, mom. She doesn't have a plasma gun, so thank heaven for small favors. Instead, she has a super-chaingun. Crap."

The Doom II Official Strategy guide has this to say about the creatures which are the fathers of the Arachnotrons: "Daddy longlegs doesn't show often in DOOM II, and when dhe does you often have some alternate methods of killing him. The boss spider has a chaingun inbedded in his face, but he has to spot and acquire you before he can fire. Fortunately, he often seems preoccupied with other matters, and is not the best at tracking a fast-moving target. Once you learn to control fluid fire and movement, this guy's is actually a lot easier to polish off than the Cyberdemons. It takes 150 plasma hits, 15 rockets, or three BFG 9000 blasts to unravel this guy's evil web.

It further goes onto say that Arachnatrons are offspring of the Spider Demon that was the final boss in the original Doom. They are nastier offensively, slinging green plasma bolts like pissed off Barons of Hell. But they can't stand the same level of damage as their daddy before going legs up.

It has since been confirmed that this comment is comic relief, and the genderless Spider Mastermind is not actually the biological mother of the Arachnotrons (this is evident in later levels where both monsters can be tricked by infighting).

The Spiderdemon is not mentioned in the Doom game booklet, presumably to avoid a spoiler. Perhaps as a result of this, the game booklet for the Depths of Doom Trilogy erroneously states that it appears in Doom II only.

Doom II RPG

 * Main article: Spider Mastermind (Doom II RPG)

In Doom II RPG, the Spiderdemon Mastermind appears as the game's second boss.

Trivia

 * The Spiderdemon bears a conceptual resemblance to Krang from the 1987 edition of Teenage Mutant Ninja Turtles. Both pilot walking machines with the difference being that the Spiderdemon's machine is a much larger and a more generic-looking quadruped.
 * In the 2012 Teenage Mutant Ninja Turtles series, there is the Kraang Spider Gunner, which seemingly completely parodies the Spider Mastermind.