The XOS-1 is an exoskeleton, appearing to be made out of the same material as the XOS-7. Judging from the number in its designation, it is the more primitive predecessor of the XOS-7, being larger and more clunky, although as it is more durable and heavily armed it may be a different model altogether. They are piloted by what appear to be Hookshot soldiers. When the mech is killed, it will fall apart, revealing the dead soldier. Unlike the XOS-7, the XOS-1 has a built in weapon, firing the same electric bolts as the energy blast bombas. The bolts are slow and can be shot out of the air. What makes them dangerous is they slowly close in on the player, and their melee will instantly kill Jason. One is met shortly after acquiring the Omega Armor, another shortly after, and 2 capture Clair and are fought at the same time. It and the AP4 Saw are the only bosses that do not appear in the finale.