Sentinels are serpentine robotic enemies in Metroid Prime: Federation Force. During M14: Tremor on Bion, they are encountered during the battle against Cyranon, a lava-dwelling machine. They serve as a diversion tactic for Cyranon, with their attacks consisting of fireballs and rocks spewed from their mouths at the Federation Force. Sentinels can be defeated, but will return for the second phase of the battle. These are gone for the third phase, however.