Metroid is the name of an asteroid converted into a mobile Pirate base. It has only appeared in the Nintendo Comics System and Captain N: The Game Master television and comics series. Since the discovery of Mother Brain's Zebesian origins, and the Chozo name for the Metroid species, it now would make sense that the enormous attack vessel was made to be named "Ultimate Warrior".
"The asteroid known as Metroid was built by Intergalactic Pirates, known as the Planteers of Krom. They designed it as a mobile attack base to strike other worlds, far beyond their home planet, Zebes."
"Metroid normally floats in space above Zebes. But, with its powerful Mega-Star Drive engines, it can be moved anywhere in the universe. Metroid's metallic surface conceals a huge array of deadly weapons, all maintained and controlled by monstrous creatures bent on galactic domination."
In the episode "Metroid, Sweet Metroid" of the Captain N television show, Metroid was seen moving towards Princess Lana's castle. It was likely using the Mega-Star Drive engines mentioned here.
"Metroid's deadliest threat, however, lies deep inside the asteroid. Here, within the endless secret corridors, dwells the smartest, most fearsome foe of all... Mother Brain."
"Mother Brain completely controls Metroid by her genius ability to program every circuit to do her bidding. But she is also dependent on Metroid; she needs the asteroid's supply of Zeebetite for power."
A number of Zebesian creatures are shown to inhabit Metroid in both the comics and television show, as well as Mother Brain. Many of these are derived from the original game and manual, albeit very loosely, in the case of the television show, which had creatures that were barely recognizable or even mostly-invented, like the Protoplasm.
|Space Stations in the Metroid series|
|† denotes a destroyed station.|
|Metroid | Sidehopper Station|
|Celestial Archives | Vesper Defense Outpost | Oubliette† | Head Shot | Outer Reach|
|Cosmos region A47|
|SR388's solar system|
|Biologic Space Laboratories research station†|
|Ceres Space Colony† | Junk Quixote | Medical Space Station | The Locker|