- Sector 3 (PYR), Sector 6 (NOC)
A powerful, mobile security robot designed to protect the station during times of biological outbreaks. The B.O.X.’s CPU contains a mixture of organic matter (possibly a brain) and advanced circuitry. Its defensive system includes thermal grenades and heat-seeking homing missiles. Despite its large size and weight, its hexapodic locomotion system allows it to move quickly and jump very long distances. Samus first encounters the robot while it is destroying parts of Sector 3, shortly after she collects Super Missile data. In the preceding battle, she damages it enough to cause it to escape. Some time after that battle, the X-Parasite infects its exposed organic components and falls under its control.
The B.O.X. is fought two times.
PART 1: When it appears in Sector 3, immediately run to the left, jump and cling to the ceiling and allow it to run past you. Depending on which side of it you are on, it will bend down and launch a thermal grenade, which creates a large moving pillar of flame when it detonates. Make sure you are far enough away from it so the trajectory of the grenade will not touch you. Right after avoiding the grenade, move so you are directly above its central body. Aim directly down, fire a single Missile, and then keep moving in the same direction. It will then try to throw another grenade at you from that side. Repeat this back-and-forth process until it decides to run away.
PART 2: When you encounter it, immediately drop a Power Bomb to reveal the grips on the ceiling, and jump to cling on to them. Fortunately, B.O.X.’s attack pattern hasn't changed much, but it is also electrically charging the water below, so don't jump in! Move far enough away from B.O.X., and it will launch its homing missiles at you. These homing missiles can be a pain, but they are easily destroyed with your normal beam, so just keep shooting them until they are gone. Then move back above its center, aim down, shoot a missile, and keep moving forward. Repeat until it explodes and reveals a Core-X. Go to this entry for more information on fighting it. After its defeat you will receive the Wave Beam.
What B.O.X. stands for has never been explained, but the acronym itself could be a reference to its box-like shape. Or, perhaps after it is infected by the X and becomes the “X-B.O.X.,” a cleverly-veiled jab at a certain powerful, but bulky game console...