This level should've been named "The Phantoon Menace".
The Metroid series is known for its monstrous enemies, but some of them deserve special mention.
- Phantoon is an extradimensional life form whose head is the only part of it that exists in normal space, the rest of it is invisible. The thing has an eye in its mouth and fires flaming ethereal eyeballs. Plus there’s multiple different possible backstories for this monstrosity. One is that it’s simply some kind of ghost haunting the wrecked ship but another is that it is the physical manifestation of Mother Brain’s evil thoughts. Another is that it stowed away on a Chozo vessel that would become the wrecked ship. In Other M’s gallery, there’s a concept artwork of what is possibly the full body and let’s just say it’s not pretty.
- Phantoon's minions on the wrecked ship, the ghostly Covern, are even freakier, appearing out of nowhere to attack and disappearing without end. They appear to be an amalgamation of skulls with rotting green flesh still attached, and are probably whatever's left of the ship's original crew after Phantoon was through with them.
- Although the entire Ing species could count, special mention goes to the Emperor Ing, the largest and most powerful of them. The swarms under its command nearly annihilated the Luminoth, feeds on the Light of Aether, and can even expose itself to phazon without harm.
- Gorea single-handedly annihilated a species of Benevolent Precursors, the Alimbics, going from a formless mass to a bastardization of their form. Even after being contained, it was powerful enough to broadcast Schmuck Bait across the galaxy to lure the hunters to its prison and release it. The thing is practically invincible, easily overpowering the other hunters and proving immune to almost any weapon.
- Phaaze is a sentient planet composed entirely of The Corruption which produces more abominations, known as Leviathans, and hurls them into space to spread phazon to other worlds. The Leviathans are powerful enough to rip space and use wormholes to travel to other worlds, and under the guidance of Dark Samus, phazon was nearly spread throughout the entire galaxy. It's implied that the planet seen is only a part of it, the rest extending into other dimensions.
- Phazon itself is somehow all interconnected, regardless of distance and Phaaze being in an alternate dimension. It appears to be a highly toxic and inanimate fuel source to conventional beings, but it clearly exhibits a will of its own in the large scale and can sometimes be heard laughing at Samus when she passes by pools of it.
- Phazon also resulted in the Chozo Ghosts. The Chozo are believed to have left the material universe, but Phazon is so toxic it dragged them back into this reality and drove them insane. So now there are psychotic and borderline invulnerable ghosts haunting Tallon IV.
- Phaaze spreads phazon via Leviathans, creatures powerful enough to travel via wormhole, something no space-faring vehicle is shown to be capable of. The things resemble a gigantic, malformed, glowing blue heart, impacting planets and spreading the corrupting influence of phazon across the entire world. The Aether Leviathan's impact was so destructive it literally broke space itself and allowed the Ing to invade. The Other Wiki compares their effect to the events in The Colour Out of Space.
- The X-parasites may not be as bizarre or cosmically powerful as other examples, but they're still completely capable of consuming all life in the galaxy. A parasite can control or consume an infected host and share that information with other X, allowing them to create freakish products of LEGO Genetics from the species of planets throughout the galaxy. Even biotechnology can be mimicked, as shown by the creation of the SA-X and the infection of various bioweapons on the BSL research station. They also demonstrate growing intelligence throughout Fusion, using the station's systems and abilities of all the life on board to fight Samus. These are the creatures the ordinarily pacifistic Chozo created the Metroids to destroy, and even with the Metroids containing the X, the Thoha wanted to destroy SR388 completely to be sure the X could never infect another planet.
- While the SA-X is usually in Humanoid Abomination form, after a certain point in its boss fight, it transforms
◊. Yes, those are replicas of Samus's head and helmet growing out of its face. - Their capacity to overwhelm a planet in minutes is best seen in Metroid Dread, where Samus unwittingly unleashes captive X, and she can only stand and stare in horror as she watches them casually float away. By the time she links back up with ADAM, he informs her that in just a few minutes, they have spread over the entire planet of ZDR, and it's safe to assume every life form she encounters has been infected and transformed into an X-based monster.
- While the SA-X is usually in Humanoid Abomination form, after a certain point in its boss fight, it transforms
