MechWarrior 4: Mercenaries puts the player in the cockpit as Spectre, a mercenary BattleMech pilot operating in the Inner Sphere during the FedCom Civil War—specifically January 3066 through July 3067. Starting with localized contracts far from the main conflict, the campaign escalates: at one point Spectre may challenge a Jade Falcon Star Colonel named Aisa Thastus, who becomes a bondsman if defeated, or die in an alternate mission route. Depending on how allegiance between House Steiner and House Davion is managed, the player ends on one of two mission paths with three possible endings.