The Pfhor are the main enemy you encounter while playing Marathon, Marathon 2: Durandal and the last in the Marathon franchise, Marathon Infinity.
Their appearance stays mainly the same throughout the trilogy- they are tall, insectoid looking, bipedal and with three eyes, red in color, arranged in a triangle about the mid to upper face. Most carry a staff weapon that shoots some sort of ball of plasma, however, there are some versions of the Pfhor warriors that are atypical and will be listed below. The color of the uniform seems to dictate the speed, accuracy and the ability of attack of the plain Pfhor warriors, as follows:
- Green — these are the slowest shooting Pfhor.
- Red — these Pfhor are a touch faster than the Green Pfhor.
- Purple — this is the break between the previous two. If you thought you could handle the Green and Red ones, these will make you wish you could go back to dealing with them. Very fast shooters.
- Blue — The fastest shooting Pfhor. Very quick, and in large numbers, very deadly.
The three atypical (by this I mean both in appearance and weapon choice) Pfhor warriors are the Troopers — armed with machine guns and pressure helmets, these are a very slight upgrade to the regular rank warrior; the Hunters are heavily armored Pfhor and have a side mounted cannon on their shoulder; lastly, there are the Juggernauts — which are huge floating tanks.
The Pfhor are slavers, most noticeably slavers of the S'pht, one of the other character groups present throughout the series of games. They control the S'pht in order to accommodate one of their other goals: the acqusition of other technology, of which the S'pht are quite skillful in doing. Of the three AI's on board the U.E.S.C. Marathon, Leela and Tycho were both dismantled and reprogramed by the Pfhor to be used for the Pfhor's own ends. Tycho later serves the Pfhor in his hunt for the AI who escaped the Marathon — Durandal.
In Marathon, the Pfhor are enslaving the people on board the ship and it is your job (a recurring theme throughout the game revolves around the question, "are you the missing Mjolnir Mark IV cyborg?") to repel the attackers. The Pfhor are eventually repelled (and the UESC Marathon destroyed), but not before taking many human slaves. You encounter the Pfhor in the last two games in the series, as well. With Durandal as your handler, your orders are to free the S'pht from the Pfhor and to further the ends of Durandal in his quest to avoid the closing of the universe.