Outside Information Trafficking

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The creature took on the host's memories, appearance, abilities, everything. It sucks everything dry. Utterly terrifying. Can you not see that if a mimic such as this were to infiltrate a population, it could replicate almost indefinitely! With evil taking the form of an ally, the galaxy could be overthrown. It is truly the worst kind of evil... it has no name, but... we call it X.

Old Bird, describing the X Parasite

X Parasite
300px-X Parasites

Artwork of the X Parasite from Metroid Fusion
OffworldClass ; ParasiteIcon
Known locales
Metroid Fusion - SR388/B.S.L.
LM (Anima) - N/A
Known worlds
Capable of infecting
and mimicking its host
Absorbed through Samus's
Fusion Suit
Featured in

The X Parasite is a unique parasite witnessed only in Metroid Fusion and the Metroid Manga.


300px-Core-X Artwork

Core-X Artwork

The appearance of an X Parasite is simple: a basketball-sized, floating gelatinous life form. The structure of their bodies allow them to slip through the tiniest crevices of any organism or synthetic surface; their soft form also allows projectiles to harmlessly pass through them (with one exception). Additionally, they have the ability to split into smaller colonies via asexual reproduction.

X are capable of infecting other organisms and mimicking their prey's DNA and memories. They do this by infecting the organism's nervous system where they then start reproducing at an exponential rate, killing the host creature in the process. Once that is accomplished, the X absorb the DNA of their host and are then able to use it to mimic their prey perfectly. Once they inhabit the body of their victim, one of the following three occurrences takes place:

  • The X mutate their host and assume complete control over its body. Uninfected creatures within the BSL station are normally docile, but all turn against Samus once an X inhabits them. X Parasites react adversely to the presence of the Metroid cells within Samus and therefore will force their hosts to attack viciously and relentlessly.
  • The X immediately digest their host, melting away its skin in a matter of seconds and leaving only its bones as remains. This occurred to a Hornoad in the Metroid Manga and presumably to Serris.
  • The X induce a coma in their host and slowly kill their victim. This occurred with Samus Aran.

Whichever the case may be, the X eventually leave their initial host in order to imitate it or to search for another host; the latter might result in the combination of multiple lifeforms' DNA (as with the Zombie researcher). The initial host's body is nevertheless consumed.

However, there are rare times when the X will ignore their prey. For example, Dachoras and Etecoons found in an X-infected area of the BSL station were left uninfected. Strangely enough, Adam suggests that the X believed these creatures were too weak or inferior for their use. It is also possible that the X were unable to open the room containing the creatures, or may have been too preoccupied with fighting Samus to try to open it.

One notable example of the X is the SA-X, or an X parasite that mimics Samus. Though the parasites in Samus's body were killed by the Metroid Vaccine, the corrupted components of her Power Suit were removed before the vaccine was administered. The SA-X was formed from those infected parts, and later broke out of its capsule on-board the BSL station with a Power Bomb, releasing all the remaining X inside and invaded the entire station.

The X can also "download" data organically, as witnessed when Samus entered the Data Room containing the Varia Suit upgrade: a Core-X was found attached to the room's central machine, where it processed the upload before destroying the equipment and fleeing to an adjacent cavern. It attempted to use the Varia Suit to protect itself, and after its defeat Samus was able to recover the upgrade herself by absorbing the X. This last ability seems to have been what drove much of the Federation's interest in the parasites.

The main predators of the X Parasites are the Metroids themselves. The X would be absorbed or "eaten" if they come into contact with a Metroid unless they are protected by a shell. To fight the metroids, the X would try to infest and then mimic a host creature capable of dealing with their predators- they are not above sacrificing some of their own in an attempt to destroy the hated predators and secure safety for the species as a whole.


Yellow XEdit


Yellow X

Yellow X are a basic type of X. When absorbed by Samus, they restore 10 units of energy. Yellow X come out of most normal enemies. A Yellow X was the X that infected Samus on SR388 after it flew out of a defeated "Hornoad".

Green XEdit


Green X

Green X appear once Samus regains her Missile Launcher. Like Yellow X, Green X come out of most enemies. When Samus absorbs a Green X, two Missiles are restored.

Red XEdit


Red X

Red X are usually only released when Gadora-X or certain variations of normal enemies (usually of a different color and harder to defeat) are killed, although they can also rarely appear from normal enemies. They are the least common non-boss X. When Samus absorbs them, they restore 500 units of Energy, 10 units of Power Bomb Ammo and 50 units of Missile Ammo.

Blue XEdit


Blue X

The Varia Suit data is here from HQ, ready to download. Get moving to a Data Room. But there's a problem... X from the sub-zero sector ARC are in Sector 6 (NOC), and they... They've been changed by the cold. If you absorb one, you'll be frozen from within. This seems like a deliberate tactic. Once you download the Varia Suit modification, you'll be out of danger. Just be extremely careful until then. The NOC Data Room is here. Remember, avoid the blue X. Use your beam to stun them in order to get by.


Blue X (called Cold X in Japanese) are blue-colored X Parasites that have been changed by the cold in Sector 5 of the BSL station. Apparently, the X did this deliberately to both stop Samus from exploring the station and kill her.Adam: The Varia Suit data is here from HQ, ready to download. Get moving to a Data Room. But there's a problem, X from the sub-zero sector ARC are in Sector 6 (NOC), and they've been changed by the cold. If you absorb one, you'll be frozen from within. This seems like a deliberate tactic. Once you download the Varia Suit modification, you'll be out of danger. Just be extremely careful until then. The NOC Data Room is here. Remember, avoid the blue X. Use your beam to stun them in order to get by. If Samus comes into contact with these X without the Varia Suit upgrade, she will unwillingly absorb them and be dealt a large amount of damage. This is due to the Metroid vaccine as Metroids are susceptible to ice, thus when she absorbs one of these X Parasite variants, she will be frozen from within. They are larger than most types of X, and they are the only kind that do not take the form of another creature.


Adam showing Samus a scan of the X Parasite.

When Samus first encounters them in Sector 6, they are eager to be absorbed by Samus, and pursue her to achieve this goal. Samus must avoid them or else face death. She can fire her beam or Missile weapons to temporarily stun the parasites, allowing her to escape in the event that she is spotted by one. Once she reaches the Data Room in the sector and defeats the Mega Core-X, she obtains the Varia Suit. When the Varia Suit is acquired, the Blue X can be safely absorbed, and they happen to restore quite a bit of energy. Immediately after obtaining the Varia Suit, several unsuspecting Blue X will fly towards Samus in the next room. After several have been absorbed, any remaining will noticeably start to avoid and fly away from Samus, and all existing Blue X within the BSL station will now flee from Samus as soon as they detect her. They can still be stunned, and recover more health for Samus than ordinary yellow X (30 instead of only 10). These only appear in Sector 5 and Sector 6.

Interestingly enough, they are much larger in size as opposed to the more common Green and Yellow X (as well as the rare Red X). Strangely, they are unaffected by the Power Bomb's vacuum ability.

History of the XEdit

200px-X Parasite

An X parasite as shown in the first volume of the Metroid manga.

Prior to the events of any Metroid game, the X Parasites evolved on SR388, where they began to greatly endanger the planet's ecosystem by throwing it out of balance. The Chozo discovered the X when they built their colonies on the planet; they were the ones who first named the organism and discovered that the X could "borrow forms from their companions". Recognizing the X's destructive potential, the Chozo created the Metroids in order to keep them at bay. This is first explained in the manual for Metroid Fusion and is later explained further in Volume 4 of the official Metroid Zero Mission Manga. Here, the Chozo refrain from telling the Galactic Federation of the X Parasites' existence, fearing that someone would view the parasite's abilities as a 'splendid technology' and use it for themselves. This fear is later realized during the events of Metroid Fusion. In Metroid II: Return of Samus, however, Samus wiped out all of the Metroids on SR388, allowing the X Parasites to make a recovery and return in Metroid Fusion.

Samus and the XEdit

As soon as the Federation ships land, the X will overwhelm them and absorb the knowledge and power of their occupants. The X are just waiting for the hunt to begin, and then they'll spread across the universe. Galactic civilization will end.

The X hunger for form, knowledge, and power. They mimic these perfectly. But they cannot copy the soul. They're single-minded, instinctively seeking to increase in number. They're a plague, and the Federation underestimates their threat.

The X must not leave here. I must destroy them all before the Federation arrives. This station has a self-destruct mechanism. I must use it to destroy the X here and on the planet. I must send them to oblivion. Them, the station, and myself, if I have to.

Samus Aran, musing on the hazards of the X Parasite

The X were first encountered on SR388 as Samus aided Biologic's research team in capturing native life forms; when Samus killed what was thought to be an ordinary Hornoad that attempted to attack the group, an X parasite came out of the carcass. The X promptly attached itself to Samus, but as she suffered no ill effects from the encounter, she thought little of it and continued escorting the researchers. However, the X soon infested Samus's central nervous system and later rendered her unconscious while she was in her gunship. Had it not been for the emergency systems in Samus's ship that automatically ejected her before the ship crashed into an asteroid belt, Samus would have died then and there. The B.S.L. scientists recovered Samus' escape pod and brought her to Galactic Federation Headquarters for treatment.

Though Samus had escaped her gunship's destruction, she was still infected by the X, which had now spread to various portions of her Power Suit, prompting the Federation medical personnel to surgically remove the infected parts. The infected pieces of the Power Suit were sent to the B.S.L. station for further study, where they would eventually become the monstrous SA-X. However, the medics could not remove the X embedded in Samus' central nervous system without killing her, and they had no way of counteracting the infection; Samus was given a very small chance of survival. Fortunately, the Galactic Federation scientists were able to devise a vaccine using a cell culture from the last infant Metroid. As the Metroids had been designed to be the perfect natural predator of the X, the parasites in Samus' body were quickly and completely eradicated by the Metroid Vaccine. As a side effect of the vaccine, Samus' genetic makeup now included Metroid DNA, granting her the ability to safely absorb the X like the Metroids could, but also leaving her exposed to the cold (A Metroid's weakness) as well as being much more vulnerable when attacked until she absorbed the Varia upgrade.

Shortly after Samus recovered from the infection, the Federation received a distress signal from the B.S.L. station. Samus was sent to investigate after the Federation provided her with a new suit, a new gunship, and a computerized CO to assist her in her investigations. Once Samus arrived, she found the station completely overrun by the X.

At numerous points, the X attempt to stop Samus in her tracks; they use methods such as hunting her down, mutating into newer, stronger forms, and intentionally destroying or blocking off Data Rooms to prevent her from recovering lost abilities. On one memorable occasion, the X went so far as to attempt to destroy the entire B.S.L. station along with Samus and themselves.

Apparent destructionEdit

At the end of this adventure, Samus flies the self-destructing Biologic Space Laboratories research station near SR388 before evacuating, destroying both the space station and the planet and presumably wiping out the X forever.

Official websiteEdit

"A parasitic virus native to SR388 that can perfectly replicate its host's powers. Initially contained for research, an explosion has released the parasite into the station's numerous breeding environments. A special vaccine allows Samus to replenish energy by collecting X Parasites."


  • Ever since the discovery of the Metroids and Chozo ruins on SR388, it was believed that the life-sucking organisms were responsible for the supposed annihilation of the Chozo inhabitants of the planet. However, with the existence of the X Parasite uncovered, the initial theory has been put in doubt, with the X now being the possible culprit.
  • Surprisingly, the Chozo, who usually have an utmost respect for all living things native to any planet they visit and do their best to not disturb the ecology, are absolutely horrified of the X Parasites and their abilities. This pushed them to create the Metroids to keep the parasites at bay.
  • In one event, the X attempted to overheat the Station, which not only could have killed Samus but also themselves. When speculating on the reason for this action, Adam states that the parasites must have felt Samus was a major threat to their entire species on SR388. The sacrifice of the X on board the BSL would have spared their brethren on the planet.
  • Despite the X having gained hacking capabilities from their human hosts, they never attempted to open all the security hatches and invade all the sectors. It is also unknown why they disabled the entire station altogether.
    • It is possible they did this to prevent Samus from doing any further damage to the rest of the species onboard the station by locking Samus out of the rest of the station. However, for some reason, the X never attempted to re-lock the security hatches. It is possible that the X never learned the location of the Security Rooms, which are not on any maps on the station, thus preventing them from locking and unlocking the different hatches.
  • The X-Parasites are similar to the Ing in a few ways. First, both can occupy the bodies of other beings, but the Ing cannot replicate/assume the form of a creature they have possessed and the X can neither directly possess organisms nor infect purely mechanical constructs. Second, they are both the menace of a higher race (the X to the Chozo, and the Ing to the Luminoth). And lastly, both have been associated with and/or copied some of Samus's abilities (the ability guardians for the Ing and the SA-X and Core-X for the X-Parasites). Though one important advantage the Ing no doubt have over the X is their capacity for possessing Metroids, the natural predator of the X. This would seem to hint that the X can only infect natural organic tissue (the Metroids were completely made artificially), while the Ing can possess any sentient or non-sentient, organic or inorganic being from the light dimension.
    • Like the Ing, the X appear to be able to infect and control deceased bioforms, as they are able to resurrect the deceased clone of Ridley and possibly Nightmare, both of which seemingly died in Metroid: Other M ; this is similar to the Ing's possession of dead Galactic Federation troopers to create Dark Troopers. It should be noted however that Ridley's clone, which was frozen at the time of X infection, was only temporarily resurrected and quickly died again shortly before the Core-X left the body, causing the body to fall apart; whether or not this was the X's intention is unknown.
    • Another major advantage that Ing have over X is that X are incapable (or very poor at) combat in their natural form, while Ing are, if anything, even more dangerous in their natural form, taking into account Dark Aether's toxic atmosphere.
  • The X-Parasites often tend to make the creatures that they mimic or infect more fearsome in appearance and often add abilities and properties that aren't found naturally in their victims. Examples of this include Neo Ridley's oversized figure and Arachnus-X's sonic blasts. These changes are likely made through DNA manipulation.
  • The X resemble a species found on Zebes in Super Metroid called Boyon. In beta trailers for Fusion, the X used recolored Boyon sprites.
  • Power Bombs can pull all free-floating X Parasites within range (except for [Cold X) into the center of the blast from the vacuum of the explosion.
  • The X are the first shape shifters ever to appear in the Metroid universe. Later characters and creatures bestowed with this ability are the Mimic in the 2002 manga, Gorea in Metroid Prime Hunters and Gandrayda Metroid Prime 3: Corruption.
    • Ironically, the X are the last to appear chronologically.
  • The alien organisms in John Carpenter's 1982 film The Thing have an identical function to the X parasites. The organisms are able to infect/absorb and mimic their victims and also mutate when threatened (albeit in a more gruesome and detailed manner).
  • During Metroid II: The Return of Samus, SR388 seemed to have a relatively low population of wildlife. The X Parasites were seemingly responsible for killing most of the bioforms inhabiting the planet, as stated by Yoshio Sakamoto and the Metroid manga. This would also explain why, in Metroid Fusion, the BSL Station's SRX (a sector that perfectly replicates the planet) contained very few of SR388's wildlife seen in the earlier game; after the extinction of Metroids, the X undoubtedly resurfaced in large numbers and steadily reduced the fauna on the planet even further (if not completely), making Galactic Federation Researchers' task of collecting varied specimens a difficult one. Whether or not Metroids also contributed to this reduction of wildlife populations before Metroid II is unknown.
  • It seems that the X are able to take the shape of inorganic materials, as seen within several creatures (Nightmare, the SA-X, Zombie researcher, the Human Core-X, and possibly the Elephant Bird). Based on the final battle with the SA-X, the inorganic components seem to actually be organic material that have taken the shape of body parts that the X can't directly infect/copy.
  • The Blue X's newfound cold nature in Fusion could have given the X Parasites back on SR388 an advantage against the mature Metroids initially inhabiting the planet. However, the planet lacked a cold climate to allow the existence of Blue X, and once they would freeze a Metroid, they would be unable to shatter it as they lacked concussive weaponry. On the other hand, a large, powerful SR388 creature (ie- Arachnus) might have given them the firepower to crush them. Even then, there would still be the problem of later Metroid stages up to and including the Queen Metroid.
  • As previously mentioned, the Blue X is larger and can be directly shot. These unnatural traits might be directly caused by its cold characteristics, such as having a more solid/thicker form than other X (logically having its liquid structure partially frozen) and an expanded body (similar to how water expands when frozen), both of which consequently make the organism more susceptible to being shot at.



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