Mystery Creature

Officially known as the Mystery Creature, this lizard-like being is the adolescent form of Ridley in Metroid: Other M.

Biology
Ridley's second form takes the appearance of a large, purple, lizard-like creature with white feathers sprouting from its back. The creature uses its long, muscular legs to dart around with great speed and force. Sharp tallons tip the ends of the creature's feet, coupled with a long, segmented tail that serves both to provide the creature balance and as a weapon; it is tipped with a sharp blade-like growth which can be used to strike and impale enemy targets. The hardy skin of the Mystery Creature deflects certain projectiles like bullets with ease. Green extremeties appear on the skin of the face, shoulders and limbs, where the hide appears to be toughest. Areas which are especially vulnerable to attack are the mouth, the tip of the tail, and underside, where the skin is weakest. Strange growths at the top of the shoulders appear to be vestigial wings, although as the adult Ridley possesses fully functional wings, they could be the emergence of these rather than their remains.

The skull of the creature is long and narrow, and the jaw is embedded with razor-sharp teeth which are perfect for pinning down and ripping apart prey. Large, orange eyes are located near the front of the skull, where most predatory creature's eyes are. It seems to possess a great deal of flexibilty and can swivel a great deal, enabling it to see at angles which would not normally be possible if facing a certain direction. Translucent eyelids also enable the creature to see whilst blinking, to allow vision of foes at all times. Finally, an unusually long tongue situated between the teeth often hangs out of the mouth, and seems to serve no other purpose other than to allow the beast to taste.

Encounters
Samus sees the creature attacking the 07th Platoon in the Biosphere Test Area from the Exam Center and runs to save them. However, when Samus arrives, the creature seems to be waiting specifically for her, hiding out of Samus' view on the wall of the building above the door she comes through, and ambushes her. It pins Samus down and attacks her with its tail and sharp teeth. The soldiers try to help her, but they are distracted by swarms of enemies including Reos and Griptians. Samus attacks the lizard's tail as it attempts to strike her head. Eventually Anthony fires a stream of plasma from his Plasma Gun at the creature, wounding and knocking it off Samus, causing the creature to go into convulsions for a few seconds. Anthony attempts to shoot at again, but it escapes by crashing through a wall which was disguised by the holographic scenery. Soon after the 07th Platoon finds Lyle Smithsonian's body ripped into shreds, Samus follows a trail of green ooze and finds the husk of the little white creature she encountered earlier, which implies that the Mystery Creature killed and ate Lyle's body after it molted from its previous form, helping it grow larger.

Samus is given orders to chase the monster, but finds only a trail of green blood. Adam instructs Samus to follow the creature to Sector 3, the Pyrosphere, though is shortly scheduled to hunt for Bottle Ships survivors in the Cryosphere, leaving the creature alone for now. Unfortunately during Samus' time in the arctic area, the beast's cries are causing the other creatures to become extremely aggressive. Much later in the game, Samus sees the creature as an empty husk stuck to a wall above a door, its back ripped open from the inside. Samus continues through the room, where she thinks that she will encounter the next stage in the creature's life. Samus meets up with Anthony again, where he is trying to fight an unseen flying creature. Samus then sees the creature and realizes that the purple monster was Ridley all along.

The fact that the creature was actually Ridley's clone in an early stage explains why it immediately tried to attack Samus when she emerged instead of attacking the soldiers, and ambushed her when it could have been fighting the soldiers, suggesting the creature may have somehow kept the memories of its predecessor. However, it is more logical to think that the Mystery Creature simply perceived Samus as the greater threat and concentrated its attacks on her.

Battle
The battle with the Mystery Creature is interesting, because it is one of the few battles where Samus is locked in first person perspective, the others being a short moment while battling the Queen Metroid, and near the end of the game when Samus is battling MB and the Desbrachians. The Mystery Creature pins Samus down and attempts to stab her with its tail as well as occasionally biting at her head. To drive off the beast, Samus must shoot Missiles at its tail, the creature's only weak spot. This is somewhat difficult, as the Mystery Creature keeps the appendage in constant motion. After the tail takes significant damage, Anthony will blast the creature off Samus.

Trivia

 * Even in his infant and adolescent stages, Ridley displays signs of high intelligence. In his second form, it had prepared an ambush for Samus, (potentially) gave orders to other bioforms and knew when to fight or retreat in battle. After he was shot by Anthony, Ridley appeared ready to attack, until he noticed that Anthony could fire the weapon again, in which he quickly retreated.
 * Ironically, in the battle with the Mystery Creature, the tail is the creature's only weakspot, while in all of Ridley's 2-D (excluding the original Metroid) and other 3-D appearances, it is one of his, or only, invulnerable spot(s). It's possible that this early vulnerability is the reason Ridley shields this area so thickly in his later stages.
 * The creature's tail and back-growths heavily resemble the Xenomorphs from Alien, a series which inspired Metroid. This makes it one of a number of creatures in the Metroid series bearing some resemblance to Xenomorphs (ie: Berserker Lords). Ridley's original appearance in Metroid also heavily resembled a Xenomorph. Samus dodging its tail is similar to the shot that takes place during the climax of Aliens, when the queen attempts to stab Ripley with her tail.
 * The way that little birdie and this creature "molted" is also very similar to the way the Xenomorph transfers to the next stage of life. Facehuggers die after they have completed their part and live on as Chestbursters, which erupt from the body of a host. Similarly, the outwards bent rib-cages on both early forms of Ridley also suggest the creature emerged in this way, but from the back rather than the chest. Additionally, the Mystery Creature's husk is stuck to the wall, which is also a tactic Xenomorphs use to restrain chestburster hosts until the chestburster emerges.
 * This creature seemed to have gone through an extreme growth spurt in a short amount of time after its molt, since its former shell is near a trail of green blood that leads to the corpse of Lyle Smithsonian in the same area where it battles Samus and the other members of the 07th Platoon. Additionally, the unlockable artwork of the Mystery Creature portrays a very small version of the lizard crawling out of the shell of little birdie.
 * It is interesting to note that after the credits, the Mystery Creature's husk is still left on the wall. It may be that the Galactic Federation saw no use in using the husk when they already have the body of the fully matured Ridley clone in their possession.