The Mystery Creature is a carnivorous purple lizard and is the second stage in the evolutionary cycle of the bio-form Ridley. Encountered in the Bottle Ship's Biosphere (Sector 1), it disrupts the Galactic Federation 07th Platoon's analysis of data pertaining to the cultivation of bioweapons. The platoon ventures outside of the Exam Center and engages the creature. As Samus joins them, the creature spies and leaps upon her from the side of the building, pinning her to the ground. It tries to stab her with its razor-sharp tail, and Samus must shoot Missiles at said tail to prevent her untimely demise. Eventually, the creature is sideswiped by a blast from Anthony Higgs' Plasma Gun, which knocks it onto its back, where it writhes in agony. After a few seconds, it regains its footing and spirals through the air and into a wall previously concealed by the hologram that is Sector 1. It is later seen in Sector 3 (the Pyrosphere) as an empty shell suspended above a doorway.