From the manual: "This boss is a mechanized terror that has led the first Alien force into the Old West. While it rumbles around on its massive treads, it will shower any unlucky souls in range with a hail of cannon shells from its weapon arm. Loaded with terrifying weapons and armored in layered in Durasteel, the Reaper is a fearsome enemy".
The Reaper is tank-like alien cyborg, which is extremely dangerous as it fires constantly. The Reaper is surprisingly quick as well and the top section of the reaper can swivel much like the turret of a tank. The arena the fight takes place in consists of an outer hallway with four entry points to the middle section where The Reaper is. The Reaper doesn't leave the big area in the middle so the player can use this to their advantage to shoot the reaper and take cover.There are quite a lot of explosive barrels in the fight so the player need's to be careful as shots from the reaper will detonate them which will almost always kill the player instantly; though this threat can be ended if the player takes out the barrels in the outer section to reduce the risk of being caught in an explosion not to mention that the Reaper will not be close enough to those barrels on the outer section so they'll be no use to the player to damage it so they may as well be taken out ; however the barrels in the middle where the Reaper is can be used to the players advantage; if the Reaper happens to be near enough to one and the player shoots the barrel this will do quite a bit of damage to the Reaper.