The Mk XII "Hydra" Multiturret is a turret equipped with two rail cannons. It operates via a targeting system, and is primerly used against enemy starships. Several can be found defending the Galactic Federation base on Norion and is most likely used to guard other Federation bases. Samus witnesses one being destroyed by a Space Pirate Fighter soon after landing on Docking Hub Alpha.
- In Greek mythology, the Lernaean Hydra (Greek: ( [Λερναία Ὕδρα] (help·info)) was an ancient nameless serpent-like chthonic water beast (as its name evinces) that possessed 9 heads— the poets mention more heads than the vase-painters could paint— and poisonous breath so virulent even her tracks were deadly. The Hydra of Lerna was killed by Heracles as one of his Twelve Labours. Its lair was the lake of Lerna in the Argolid, though archaeology has borne out the myth that the sacred site was older even than the Mycenaean city of Argos, for Lerna was the site of the myth of the Danaids. Beneath the waters was an entrance to the Underworld, and the Hydra was its guardian.
- "XII" is the Roman numeral for the number 12. This may refer to the Twelve Labors.