Torizo

It seems that the Torizo are sentinels hand-crafted by the Chozo. This is evinced by the Chozo Lore, Statuary in Metroid Prime. They are likely bio-mechanical, as the Torizo are capable of doing things that would otherwise be impossible. For example, they are capable of firing spherical projectile from their mouths. (The Gold Torizo is able to fire projectile from its chest, as well as fire beams from its eyes and hands.) Also, in the first battle, when the Torizo loses its head, it bleeds and moves frantically, yet does not perish.

Trivia
The theme played for the Torizo is the same as Ridley's.