Proteus Ridley

Proteus Ridley is the unexpected final boss of Metroid: Samus Returns.

Background
Following his defeats as Meta and Omega Ridley in Metroid Prime 3: Corruption, Ridley seemingly managed to regenerate most of his original body and removed large portions of his cybernetics.

Presumably, he was dispatched to SR388 when the Space Pirates became aware of Samus's mission to exterminate the Metroid species. By the time he arrived however, she had destroyed all but one of them. As Samus is preparing to leave SR388 with the baby, a newly hatched Infant Metroid that imprinted onto her, Proteus Ridley unexpectedly arrives and proceeds to capture the Metroid with the intention of bringing it to the rebuilt Space Pirate fortress on planet Zebes. As if foreshadowing Ridley's appearance, a thunderstorm (accompanied by unsettling music) began as Samus and the baby arrived at the Surface after leaving Area 8. A cave-in blocks off the initial entrance to the main caverns, preventing access to the landing site from the opposite side. Facing her Gunship on the top of a cliff, Samus activates it remotely while the baby curiously approaches it. From a distance above, Proteus Ridley emerges out of the storm clouds and heads straight for the Metroid; at the sight of her nemesis, Samus hurries in his direction to intervene. He briefly chases the baby, landing on top of Gunship, before successfully catching it with his left hand, holding it firmly as he is confronted by Samus.

First phase
Starting off in the air, Ridley clutches the baby in his metal hand as he battles Samus. His attacks include breathing five purple fire balls in an arc, thrusting his tail below him in an attempt to jab Samus, and quickly slamming onto the ground before taking flight again. If Samus is Space Jumping at his height and above, or climbing the wall with the Spider Ball, Ridley will whip his tail in a wide arc directly in front of him and alter the angle of his fire balls. Ridley's attacks are very powerful, with many taking out a full Energy Tank. His weak point is both his chest and mouth area, which Samus can take advantage of using Super Missiles, Plasma Beam shots or the Beam Burst. Regular Missiles are ineffective as they will merely bounce off of him. After taking enough damage, Ridley will recoil and release plenty of Aeion Orbs to refill Samus's Gauge. The Plasma Beam and Ice Beam can also damage his chest and mouth areas, though the Plasma Beam causes more damage. However the Grapple Beam is ineffective and inflicts no damage at all, even if it his weak points. While Super Missiles are effective, Samus may wish to save them for later phases, as Ridley's flying makes him somewhat harder to hit.

Phase Transition Cutscene 1
As he attempts to fly away with the Metroid in hand, Samus jumps onto his tail. Ridley shakes her off of him, but she immediately flies onto his chest with her thrusters and pumps Plasma Beam shots into him (interestingly Samus will fire Plasma Beams, even if her arm cannon is in the Ice Beam or Grapple Beam configuration, as the Plasma Beam shots are scripted to appear by default). He screams out in pain and releases the baby, prompting Samus to jump towards and grab the Metroid as she falls away from Ridley. As he attempts to charge at her, she lands a beam shot on his left wing, sending him crashing into the nearby cliffside and is partially buried under rubble. At first it seems Ridley was killed in the crash, however his eye opens revealing he was only knocked out. Ridley breaks free of the rubble and rises up. Samus jumps down from top of the Gunship where she landed after grabbing the Baby which she lets go of to focus on defeating Ridley. After landing Samus rushes forward to confront Ridley who jumps down to confront Samus once more, though this time on the ground as his wings were apparently damaged by Samus' attack and the subsequent crash and fall. After roaring at her in anger for damaging him and rescuing Baby, Ridley engages Samus again for the 2nd phase.

Second phase
In the second phase, the baby watches the battle at a distance near Samus's Gunship as a storm intensifies causing a tornado to rage in distance as if to signify the increased intensity of the battle. Ridley will now have additional attacks, some of which are ground-based. When he is located on the ground, he will shoot individual blasts of fire at Samus' position and swipe with his claws if she is close to him; with the latter attack, Ridley may follow up with a second swipe. He takes flight if Samus jumps over him, from which point he will use the previous aerial attacks along with two new ones. One of new attacks consists of Ridley charging across the area with his entire body and tail extended to the floor, giving this move a wide range. If Samus is close to a wall, he will slam against it and remain still very briefly, but if the wall if sufficiently distant he will merely turn around. The second new attack is Ridley swooping in an attempt to grab Samus which, if successful, will trigger a short cutscene where he slams her repeatedly onto a wall before tossing her. This sequence causes high amounts of damage to her, but can be negated if Samus has the Lightning Armor active; in fact, the ability can be turned on at any moment during the cutscene, but will not remove any damage inflicted prior to its activation. Two of Ridley's aerial attacks from the 1st phase have different properties, such as the tail thrust which now stabs into the ground and releases a wave of spiked rocks when he pulls it out. His ground slam no longer has him take flight right after and instead switches him to his ground-based pattern.

Phase Transition Cutscene 2
Once he has taken more damage, more Aeion Orbs will be released from Ridley. He attempts to stab Samus with his tail before shielding himself against her attacks as he flies towards her, getting close enough to grab and throw her at a wall. He then pins her on the floor with his left hand and shoots a fire ball at point-blank range, exhausting her. Before Ridley can continue, the Infant Metroid intervenes to save its "mother" and leeches some of his Life energy, but the latter is quickly shaken off. The baby transfers the absorbed energy to Samus, which restores part of her health (equivalent to 2 full energy tanks) before the third phase.

Third Phase
Ridley becomes more aggressive, using all of his previous attacks at a faster rate as Samus continues to battle him with assistance from the baby. He gains two additional attacks: on the ground, he will use an immensely powerful claw slash that leaves an afterimage on screen, while on the air he will shoot a focused fire ball directly under him which releases fire shock-waves on both sides from the point of impact. Additionally one of Ridley's most devastating attacks appears during this phase. Proteus Ridley reels back with his hands out and open, then lunges forward and if he makes contact with Samus, he grabs and smashes her against the wall dealing incredible damage. To avoid this grab attack, Samus must Space Jump as soon as she sees him reel back which acts as a tell that he is about to perform the grab attack.

Final Phase Transition Cutscene
After Samus inflicts a certain amount of damage to Ridley during the third phase the baby helps Samus again by draining more energy from Ridley and transferring it to Samus. This leads to 4th and final phase.

Final Phase
During the Final Phase, the only way to defeat Ridley is by parrying Ridley's counterable attack with a Melee Counter. It should be noted that Ridley automatically performs this attack at the start of the final phase which is the only time during the final phase in which he is guaranteed to perform it, as he performs it randomly for the rest of this phase if Samus fails to parry it the first time. It should also be noted that during the final phase, damaging Ridley until he drops resources such as Aeion Orbs will not trigger another phase, instead Ridley's skin reverts to its purple hue and Samus will continue to fight through the phase until she successfully performs a Melee Counter to parry Ridley's counterable attack.

When performing his counterable attack, his mouth emits the standard white ring that indicates a counterable attack, but there is nearly no time to do anything but counter if Samus is in range to do so when he lunges forward. This forward lunge covers a good distance, so if Samus is not in a position to land a successful Melee Counter, it is best to Space Jump and avoid it, then wait for Ridley to perform it again.

End Battle Cutscene
Successfully parrying his attack with a Melee Counter triggers a cutscene where she blasts Ridley in the chest several times with a weapon of her choice, and then climbs up his body before repeatedly shooting down his throat. Ultimately, both Samus and the baby are able to defeat him, causing Proteus Ridley's cybernetic implants to short-circuit before he falls to the floor subdued.

Aftermath
Samus watches an unconscious Ridley before she looks over to the Infant Metroid, prompting her to leave with it in the direction of her ship. Though he is not seen again afterwards in the game, he either regained conscious offscreen or was recovered by Space Pirates, as a Hornoad is seen after the credits gnawing on Ridley's abandoned mechanical claw.

Based on his following appearance in Super Metroid, and to some extent the abandoned mechanical claw in the ending, he removes the rest of his cybernetics before attacking the Ceres Space Colony, where Samus donated the baby Metroid for research. Ridley would rampage the station, and with his organic body restored successfully abduct the baby, bringing it to the Pirates' lair on planet Zebes leading to the Final Conflict that lead to the deaths of Ridley, Kraid, Mother Brain, and Baby. However ironically both Ridley and the Baby would be cloned by a corrupt faction within Federation from DNA obtained from Samus' Power Suit. Samus would confront both clones, though Ridley's managed to escape and was killed by Baby's clone which had matured into a Queen Metroid and its remains where later recovered by the Federation who kept it in cold storage in the B.S.L. station where it was later infected by the X Parasites resulting in the creation of Neo-Ridley. However Samus who had gained the Metroid ability to absorb X Parasites after being cured of her X infection using cells from the Baby. Samus defeated Neo-Ridley and absorbs its Core-X regaining her Screw Attack ability.

Metroid: Samus Returns Official Guide

 * Inhabitants & Eco System of SR388 (p. 23)
 * PROTEUS RIDLEY
 * "Samus' greatest nemesis makes a return in this game to put a stop to her Metroid eradication. It was Proteus Ridley, Mother Brain, and the Space Pirates that harnessed Metroids for evil during Samus' first mission, and they clearly found it to their liking. Proteus Ridley’s not about to allow Samus to wipe out such a formidable source of power and an equally devastating weapon—not without a fight."

Trivia

 * Proteus Ridley's visual appearance reflects the progressive regeneration of his organic body. This process was first noticeable with his Omega Ridley form, where his purple body became more pronounced and was pushing off the implants he gained as Meta Ridley back in the first Metroid Prime.
 * Consequently, Proteus Ridley and his later form in Super Metroid have lost much (in the latter case, all) of the protection the metal implants offered throughout the Metroid Prime series, as he can now be harmed by mere Beam weapons shot directly into his exposed organic body.
 * Owing to him being a variation of Meta Ridley, several of Proteus Ridley's vocal sound effects are recycled from his Meta form, as well as his mouth and chest weak points.
 * Ridley was not originally present in Metroid II: Return of Samus, of which Samus Returns is a remake. Thus his appearance in the game can be considered a recon. Proteus Ridley is one of two original bosses in Samus Returns, the other being the Chozo excavation robot Diggernaut. Along with Diggernaut and Arachnus, Proteus Ridley is one of the few bosses in Samus Returns that is not a type of Metroid.
 * Samus Returns marks the first time that Ridley has been the final boss of a Metroid game; while Zero Mission featured the Ridley Robot as its final boss, it was merely a robot he built in his likeness.
 * His presence in the game was first hinted at in the Overview Trailer, where Proteus Ridley's theme was heard during the Aeion gameplay portion. A glimpse of his hand was also seen in the September 13, 2017 Nintendo Direct, two days before the game's release, with the narrator also hinting at his identity by saying "Vengeance has a name".
 * The Metroid: Samus Returns Official Guide erroneously claims that Ridley has been known as "Proteus Ridley" since before Samus became a Bounty Hunter.
 * In Greek mythology, Proteus is the name of the god of rivers and oceanic bodies of water, who was known for his adaptability and versatility. Therefore, the Proteus name for Ridley is appropriate on two aspects: the reputation he likely obtained prior to Samus's career as a Bounty Hunter, and Ridley's form in Samus Returns as it reflects his ability to easily recover from his battle wounds.
 * There are several moments in the Proteus Ridley battle that reference several scenes from previous games:
 * The climax of Super Metroid, in which the mutated baby saves Samus by draining Mother Brain and transferring the energy to the former, is referenced when the baby drains Proteus Ridley and heals an injured Samus before he could kill her.
 * The confrontation with Ridley's adolescent clone in Metroid: Other M, in which he pins Samus to the ground until she is saved by Anthony Higgs, is played out in a similar fashion when Proteus Ridley pins down Samus until the baby's intervention.
 * The free-fall battle with Meta Ridley in Metroid Prime 3: Corruption, where she mounts his head and fires Power Beam shots down his throat, is referenced whenever Samus successfully Melee Counters Proteus Ridley and shoots directly into his mouth with a weapon of her choice.
 * Meta Ridley's defeat in Metroid Prime. Both Proteus Ridley and his Meta form flail at the end of their battles as a result of their body being overwhelmed with electricity.


 * The Baby contributing to Proteus Ridley's defeat foreshadows future acts the Metroid indirectly performs that also lead to the defeat of Ridley's future incarnations. In Other M, the clone of the Baby grows into a Queen and kills Ridley's clone by absorbing his life energy. In Metroid Fusion, the Baby's DNA is infused within Samus to protect her against X Parasites, and is what ultimately helps her prevail against Neo Ridley, an X Parasite-imitation of Ridley.
 * If Samus dies at any point during the battle, she will have to restart the entire fight from the beginning.
 * Proteus Ridley is one of the most difficult bosses in the game; on Fusion Mode his slashing attack wich leaves an afterimage is enough to take three Energy Tanks off of Samus's overall health.
 * Proteus Ridley's theme is altered for each phase of the battle. The first is a remix that combines notes from Vs. Meta Ridley, the version from the Prime Series, and Nemesis Ridley, the version from Metroid: Other M (heard here). In the second phase, his theme has an edgier tone with a more tense opening similar to Ridley's themes in Metroid: Zero Mission and Super Metroid (heard here). The final phase retains the tension but with a slower tempo, similar to that of Neo-Ridley's theme from Metroid Fusion (heard here).
 * In his official artwork, his neck is still primarily cybernetic and he also has a cybernetic lower jaw. In the actual game, however, only the back of his neck has any cybernetics.