Arachnotron

"Maybe cybernetics wasn't such a great idea after all. Look what the demons have done with it. It seems unfair somehow you're not the only guy in Hell with a plasma gun."

- Description in the Doom II manual

"They are the small 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."

- Description in the Doom II Official Strategy Guide

The Arachnotron is a spider-like cyborg monster introduced in Doom II. It is similar in appearance to the Spiderdemon, but smaller and with large eyes that change color depending on the monster's current state (moving, hurt, or attacking). It is supported by a metal chassis and a body that consists primarily of a large brain, along with two small arms. Instead of a chaingun, it wields a powerful plasma gun that fires bursts of yellow and green energy.

Doom 3
The designers considered reintroducing the Arachnotron for this sequel, but cut the enemy for unconfirmed reasons. No code or 3D model are known to exist.