Trocra are crystallized colonies of cyanobacteria that float in the air. They were found at regular intervals around the room that held the first battle between Gorea and Samus, in the Oubliette. When touched, they will explode, doing damage. Trocra proved useful to both Samus and Gorea, as Samus could destroy them for items, and later Gorea's Seal Sphere grabbed them with energy tendrils and hurled them at Samus, though they could be easily sidestepped.