The Quad is a Luminoth combat mechanoid created to fend off the Ing invasion force during the early years of the Ing/Luminoth war. Many were possessed by the Ing after they had learned how to control mechanoids. Those that remained malfunctioned and went rogue, turning against all life forms. Quads are commonly found in the Sanctuary Fortress, a huge Luminoth structure that stood above what looks like a sprawling metropolis.
Quads are unique because of a clever feature in their design. A Quad is made from two robots, one that holds the command module that forms the head, and the other forming the main body composed of the chassis and legs. They can function individually or as a whole, and when one of them is destroyed, the other continues to fight until an active replacement can be used. The Quad's primary attacks include slashing with its sharp bladed legs, a ramming attack while spinning, and an energy beam from its head. When it fires the beam or when Samus rams it with the Boost Ball while it is spinning, a cooling rod extends from a heat sink underneath the chassis. Hitting it with the Boost Ball will destroy the main body, leaving the Quad CM to its own devices. The Quad's CM is just as dangerous as when it was attached to the body, however. It has a variable energy shield that alternates between Light and Dark energy. Using a beam with the polar opposite of the shield's energy(Light Beam on Dark Shield, Dark Beam on Light Shield, Annihilator Beam on both) will disable it quickly, allowing Samus to blast it apart with a powerful attack.
- Metroid Prime 2: Echoes (First appearance)