Dr. Kelvin

Dr. Kelvin is a scientist working for the UAC on Mars. His assistant is Jenkins.

Plot
Dr. Kelvin is first found in Sector 4 (Doom RPG), where he is struggling to open a locked door, finally deciding to blast it open by asking the player to fire at barrels that have been placed by Jenkins. This has no effect and only results in the computer controlling the door mocking the player with the message, "HAHAHA! You thought you could blow me up?!?!", until the mysterious appearance of Dr. Guerard, who manages to open the door.

Dr. Kelvin assists the player several times throughout the game, for instance when the player needs to be teleported to the other side of a lab in Sector 7. He is last encountered at the destroyed Junction after the second attack, when guarding the door that leads to the Reactor. He tries to prevent more monsters from getting inside. At the moment the player gets the door open, Dr. Kelvin says, "One of those things got inside of me. I can feel it." He then transforms into a monster. The monster has to be eliminated by the player before exiting the level. Kelvin's transformation can be avoided however, by simply not speaking with him after opening the door.