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.
It is unclear why the Trocra appeared in the Seal Sphere room; the Alimbics could have placed them there as a defence against anyone who might want to release Gorea. However, all seven Bounty Hunters were able to get to the Seal Sphere without any hindrance.
- As evidenced by the model's file name "PowerBomb_Model", the Trocra was originally intended to be a Power Bomb, although this was scrapped for unknown reasons.