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Your duty has always been to die, soldier!
~ Sabaoth in Doom 3

Sabaoth is a monster from hell and is the third boss in Doom 3. He is encountered in the level Central Processing: Primary Server Bank in the CPU chamber of UAC. Sabaoth is a mobile arsenal with enough firepower to topple even the hardiest marine.


Sabaoth's lower half body has been replaced with a tank frame, while the upper portion is a humanoid body attached to heavy machinery armed with a very sharp claw and a shoulder-mounted BFG. Sabaoth is rather large, being slightly taller than a Hell Knight and significantly wider. His melee attack is claw strike (which makes getting close to Sabaoth unwise), and his BFG-9000 deals a massive damage. Sabaoth fires a BFG shot every several seconds or so. The BFG projectiles constantly emit secondary energy beams which deal continuous damage. His BFG was taken from Jack Campbell. In spite of his powerful mechanical body he can not run the marine over with his tank treads.


Sabaoth is really Sergeant Kelly after his demonic transformation.

He was at the top of the enlisted chain of command on the Mars Base (Marine HQ). Though stoic and cold, he is very well respected for his dedication. A career military man, he only expects the best from his men. He gets easily agitated when his men slacks on his efforts, and typically relegates slacking marines to the worst duties as punishment. Not long after, the demonic outbreak occurs killing (and possessing) almost everyone on the entire base. Sergeant Kelly, at that time was in Delta Labs, orders all remaining marines to head back to HQ for further orders. Only the protagonist marine survived to arrive at HQ alive. Kelly seemed both surprised and relieved to see the marine and from that point on he gives his sole surviving marine instructions and gives missions.

After some time later the marine is not contacted by Kelly again until he reaches Delta Labs. Kelly appears on a monitor in a recorded message and tells the player to meet him at Service Tunnel 1.

That would be the last contact with Kelly the human.

When the marine gets there, Kelly is nowhere to be found. After this, the marine does not see or hear from Kelly again until the CPU Complex. When the marine met with Kelly, Kelly had become something other than a human.

From Kelly to Sabaoth

How did Kelly become an abominable fusion of flesh and machine still remains unknown. While some affirm he was working with Betruger and the demons since the beginning (supported by the fact that he insisted in contacting the Earth armada to bring them to Mars, knowing it would be taken over by the demons, and by his phrase, "Your duty has ALWAYS been to die, soldier!"), others think he was captured, mind-broken and transformed by Betruger to serve him, and that his zealous attempts at contacting the fleet to get reinforcements were simply basic military logic (realizing that the battle is lost without reinforcements). It is also worth noting that Jonathan Ishii, a scientist and part of the Delta Science Team who is unlikely to have been allied with Betruger, was attempting to send a distress signal before the hell's invasion, opening some possibility to the latter interpretation.

Anyhow, what is certain is that at some point during the game, Kelly is converted over to the side of hell and proceeded to injure Eliot Swann and Jack Campbell. The marine makes his way to the CPU complex. Before succumbing to his wounds, Campbell tells the marine that Kelly has his gun. At this point, Kelly contacts the marine and taunts him saying: "I killed that pathetic bodyguard, and now I shall kill you."

The marine comes face-to-face with Kelly, who has been transformed into Sabaoth. The marine has no choice but to fight and kill his former commanding officer.


  • Although Kelly doesn't appear in Resurrection of Evil, his office can be found, where he kept a double-barreled shotgun. Interestingly, there is a picture of him killing a bear with his shotgun, as well as having the trophy of the same bear mounted on his wall.
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