Metroid is the heroine, Samus Aran is a galactic bounty hunter. She wears an exceptionally powerful and adaptable exoskeleton created by the ancient Chozo race. Costume upgrades collected during playthrough are not carried over to the next part of the game, so they must be collected again in each part. Metroids are large, jelly-like creatures with four cell nuclei. They can suck the life energy from any living organism, in the process of which the victim usually dies.