Tourian

Tourian is the final region of Zebes encountered by Samus in Metroid, Super Metroid, and Metroid's remake, Zero Mission. In each of these games, Tourian is the location of the primary antagonist, Mother Brain, as well as the majority of the Metroid (species)s. Tourian is distinctly different than the other regions of Zebes, in that it is largely composed of metal, giving the indication that it was built, rather than having naturally existed. Though bearing the same name, the Tourian visited in both Metroid and Zero Mission is not the same as its counterpart in Super Metroid.

Metroid and Zero Mission

Though their maps vary to some extent, Metroid and Zero Mission feature comparable maps, with Tourian located in roughly the same place in both. In both games, the entry point to Tourian is reached by ascending a tall shaft east of the staring point in Brinstar, and travelling westward from there. There, a barrier blocks the way, and it can only be opened by the defeat of Kraid and Ridley in their respective hideouts. After the barrier, an elevator leading down to Tourian can be accessed.

Tourian is a series of long hallways with doors of various levels blocking the way, requiring the use of Missles to proceed. Throughout Tourian, Rinkas constantly appear to stall Samus' progress, implying a defense system.

While there are no Space Pirates in Metroid's Tourian, Zero Mission contains the bodies of dead Space Pirates, implying that they were killed by the Metroids. In the original, Metroids are always visible in the foreground, and killing them is not required. In Zero Mission, Metroids appear from the background, and must be exterminated before the next room can be accessed. This is accomplished by freezing them with the Ice Beam and shooting them with Missles.

Mother Brain, protected by five barriers of Zebetite is the final boss encountered by Samus in Tourian. However, upon defeating Mother Brain, Samus is required to flee through a long, upward escape shaft, leading to the surface of Zebes.

Super Metroid

In Super Metroid, Tourian's location has changed, and it is no longer accessed through the upper areas of Brinstar. Instead, an elevator in the western parts of Crateria, which comprises the surface and top layers of Zebes, is its entry point.

This elevator shaft is sealed by the Golden Statue, and cannot be accessed until four bossess are defated. Kraid and Ridley again stand in between Samus and Tourian, but this time, Phantoon and Draygon must also be killed in order for Samus to advance.