Sector Zero(セクターZEROSekutā Zero) was a mostly unexplorable area of the BOTTLE SHIP, designed after Tourian. The entrance can still be reached through an elevator in the Cryosphere. This sector contained Metroids, most of which were genetically altered to be unfreezable, as well as MB's original body, the latter within the Section 4 Gravity Block. MB's new body informed Samus of it while she was posing as Madeline Bergman, though she did not mention the unfreezable aspect of the Metroids.