Sergeant Swann is the intelligence specialist that briefed the Marine before the invasion on the Earth Spaceport in Doom II, and other missions throughout the campaign including his battles through the streets, and into Hell itself to stop the invasion of Earth.
Behind the scenes
Doom 3 includes a character named Elliot Swann. It's probably a nod to Andrew Swann who is mentioned in the acknowledgements.
- Doom II: The Official Strategy Guide, pg 53