Marathon EVIL is a scenario for the Marathon Infinity Game engine.
Marathon EVIL is a scenario for Marathon Infinity, originally released in 1997. It features 17 new solo levels; 22 new network maps; and new enemies, sounds, textures and weapons. A chief difficulty is the low amounts of ammunition available, resulting in a greater reliance on melee weapons, such as fists or staff.
Storyline
Marathon Evil is a sequel to a Marathon 2 single player mission called "Siege of Nor'khor" by the same author. In this new installment the player must trace the ship that he had disabled, but which had mysteriously vanished before its complete destruction. After finding it crashed on a small abandoned moon, the player finds another much older Pfhor ship hidden at the bottom of a lake, and, visiting it, inadvertently awakens a very ancient, taboo superior caste of the Pfhor called the Mystiques, which remained hidden for eons while watching over the lower castes of their race, regarding them as their young and naive offspring and helping them behind the scenes on occasions. The player must then infiltrate the Mystiques' moon and stop them from going back in time, or else they will be able to intervene and help the Pfhor enslave both the humans and the S'pht.
http://bighouse.bungie.org/evil/