The theme is named after the life force of Mother Brain, the Zebetite. It begins playing as soon as Samus enters the Zebesian Command Center. In Zero Mission, it also plays as Samus is descending into Norfair for the first time, during a cutscene where Mother Brain watches her from the Zebesian Command Center.
Zebetite is a tense theme that has very little discernible melody and a chromatic chord progression. The original is composed using a set of two different sound effects rapidly playing together, likely intended to give the listener a feel of simultaneous urgency and unsettling discomfort. The Zero Mission version is faithful to the original, though the more electronic instrumentation and the more simplistic, less chaotic arrangement gives it a pulsing and alien-sounding vibe.
- The Mother Brain theme from Super Metroid also makes use of a chromatic chord progression in its harmony, seemingly as a reference to the original Zebetite theme.
- The Aurora Unit 313 theme in Metroid Prime 3: Corruption, while a remix of Darkness, is arranged in such a way to resemble Zebetite. The boss itself resembles Mother Brain to a great degree in terms of physical appearance and attacks. The Ship Down theme also sounds similar to Zebetite.