Dr. Elizabeth McNeil

Dr.Elizabeth McNeil is a UAC Mars Facility Delta Labs researcher, and the one who blew the whistle on Dr. Betruger's research in Doom 3. She is also the one who asks the UAC board to send Swann and Campbell to the base to investigate the experiments Betruger is running. Although she is not seen in Doom 3, due to Betruger sending her off the planet for her actions, her PDA is left in her office and details her response to the experiments going on in the base and the actions she takes as a result.

Doom 3
Dr. McNeil is first mentioned in Doom 3, where a message from her is on the PDA of the woman who transforms into a Lost Soul. Her own PDA can be found in the Delta Lab, containing an e-mail from Councilor Swann informing her that he is coming to Mars to investigate her concerns about Dr. Betruger.

Doom 3: Resurrection of Evil
McNeil appears in Resurrection of Evil, as the player's commander and source of tactical intel. Elizabeth was assigned in the abandoned Mars facility to lead the primary assessment of the abandoned research facilities on Mars. She is first seen in the command center asking a marine about the status of the recon squad, including the protagonist, in the underground ruins beneath the base. During the invasion she was able to escape Eriadu facility and get to a sealed office in Phobos Labs. She informs the marine protagonist of the situation and orders him to rendezvous with her in the labs. When the Marine gets there, Elizabeth informs him of the true nature of The Artifact, a one way portal generator from Hell. According to ancient Martian writings found and deciphered in the ruins, it can only be destroyed by bringing it to its source in the next world. McNeil determines that four system generators must be shut down in Phobos labs in order to bring a teleporter to Hell online. By this time, McNeil had also discovered Betruger's command of the new invasion.

Late in game, Dr. McNeil orders the marine protagonist shut down life support systems to the base in order to power the teleporter long enough to allow the marine to get to Hell. She selflessly declared that their mission was "more important than any of us." Soon after this, the Marine loses contact with her, presumably due to her death. In a final cutscene the screen fades to white, and McNeil can be heard saying: "Marine...? Marine... Welcome home." implying they are both in a better place after having sacrificed themselves for humanity.