Duskdude

Duskdude, also referred to as the Intruder, is the main character of DUSK. Duskdude serves as the embodiment of the player and very little is known about his background.

Appearance
Duskdude's canon appearance is only revealed through the comics & the ending of the game. He is a tall, old man with a long, white beard, a brown trench coat or duster & hat. The rest of his appearance is generally disclosed.

Lore
Level design hints at some story behind Duskdude's origins, but most of it is left unclear in the game itself. However, in the Steam forums the developers have clarified that he was a resident of DUSK, Pennsylvania and during his absence, for an unknown reason or period of time, The Cult became prominent in the town and sacrificed members of his family for opposing them. The level design of E3M7: Homecoming implies what may have happened to his spouse and child. Both presumably being killed in their house burning down, due to the sound of crackling flames and screams that are heard when entering the home, indicated by his comments "Why am I here?" and "It hurts to remember" when their photos are examined. (Prior to this confirmation, he was speculated by some to be a treasure hunter who sought the town in hopes of becoming rich, only to end up clashing with the cult.)

Duskdude may also have a fear of or hatred towards frogs. Interacting with the cellar door outside of Duskdude's house in E3M7: Homecoming prompts him to say "Don't want to go down there. Too many frogs." This may tie in the appearance of the Horrors, which appear to have amphibian traits and otherwise may be the physical embodiment of Duskdude's fear of or hatred towards frogs.

Trivia

 * Duskdude's appearance is similar to that of Caleb from the 1997 Monolith Productions game known as Blood.
 * Duskdude when interacting with a computer will comment "Don't have time to play with myself," which not only serves as an innuendo, but maybe also as a fourth wall break. This is also a reference to Duke Nukem 3D, a game by 3D Realms(formerly Apogee), where when the player interacts with an arcade machine featuring Duke Nukem 2, Duke will remark "Don't have time to play with myself."
 * Duskdude hates Rats. As blatantly stated by his comment "I hate rats..." in E3MS: The Ratacombs after killing One As Many.