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

The X Parasite, also known as Unidentified Parasite Creature-X by the Federation[1] and known as Eddis by the Chozo,[note 1] is an extremely hostile, shape-shifting organism native to planet SR388. They appear in Metroid Fusion, Metroid: Samus Returns, Metroid Dread, and the prequel manga. They serve as the secondary antagonist of Fusion and the tertiary antagonist of Dread.

X Parasites are able to assimilate both the DNA and knowledge of other life forms, as well as to incorporate those features when they take new hosts, and their single-minded drive to consume and spread leaves them a threat to all other life in the cosmos, making it urgent to eradicate them.

The extreme danger of the X Parasites is what led the ancient Chozo to design the titular Metroid species, precipitating the events of the series. The galaxy at large learns of the Parasites in Metroid Fusion after Samus successfully eradicated the Metroids on their homeworld in Metroid: Samus Returns, and the detection of surviving X on ZDR in Metroid Dread forces Samus to once again confirm their extinction. Despite this risk, the extreme versatility of the X Parasite has led some among the Chozo and Galactic Federation to show interest in them as potential resources.

Biology and characteristics[]

An X Parasite scanned by a security sensor.

An X Parasite's base form is a simplistic, airborne gelatinous organism approximately the size of a basketball with three particle-like structures that circulates within their mass like electrons. Their gelatinous bodies allow them to slip through the tiniest openings and, with few exceptions, harmlessly yield to projectiles. X Parasites reproduce rapidly and asexually, allowing them to quickly infest entire planets if not contained, and even in their base form they are able to quickly pursue and infect their prey. While X are incredibly mobile, base form X can still generally be contained, such as by using the vacuum of a Power Bomb to suck them in.

X Parasites are voracious, and once they locate prey, they infect the organism's nervous system and start reproducing at an exponential rate, consuming the host's soft tissue within seconds. It is during this process that the X absorb the DNA and memories of their victim, allowing them to replicate it and further their species's existence; this process is not prevented even if the host was already dead prior to infection. Depending on the situation, the Parasites may either begin mimicking the host's structure then and there, giving the appearance that the host has been possessed, or may simply consume it and create a facsimile at a more advantageous location. Via unknown means, Samus Aran was able to resist her own infection and slip it into a coma, allowing her to survive until the Metroid vaccine was administered. However, the X Parasite was still able to acquire her genetic and memetic information, producing the SA-X. The X Parasites are not limited to purely organic lifeforms—they are able to consume and replicate bio-mechanical technology, such as Samus's Power Suit or Security Robot B.O.X.'s neural network, and can even interface with technology to "download" similar data, as in the case of the Barrier Core-X. On a similar note, they can even copy DNA from fragments of an individual, which is demonstrated with the creation of the SA-X from surgically-removed portions of Samus's Power Suit, with it also being implied in the case of the Kraid-based portions of Raven Beak X that Kraid's DNA came from the ejected spike from Kraid before the latter sank into the lava. However, they are incapable of infecting of inorganic creatures, with E.M.M.I., Robot Chozo Soldiers, and other mechanical beings remaining uninfected throughout Samus's journey on ZDR.

X Parasites are proficient at mimicking their prior hosts, allowing them to blend in and strike new, unsuspecting prey, which helps address the natural aversion of SR388's wildlife to their base form. However, X Parasites mimicking Chozo have blank white eyes instead of their natural color; this trait is shared with SA-X, who would also have had Chozo DNA. X Parasites retain the information acquired from previous hosts and will often combine information from various sources to produce new forms more suited for combat; in a general sense, most X forms of wildlife possess more dangerous features than their source. Examples of this include Neo Ridley's oversized figure and Dessgeega's spike blasts. When X find themselves in danger or lose a fight, they will often incorporate features from a specific additional source. For instance, when Samus Aran was able to overwhelm an SA-X, it mutated into a more powerful, monstrous form that incorporated material from a previous Hornoad victim. On ZDR, the X went even further, fusing several sources with the form of Raven Beak into one behemoth hulk. Several of the Chozo soldiers of the Mawkin tribe also demonstrated the ability to mutate when on the losing end, such as having their eyes vanish and have their heads split into a gaping maw. However, it's unclear whether this was an extension of their ability to incorporate features from prior infected hosts or a wholly unique condition for ZDR X. When an X Parasite hive's manifestation is destroyed and they are reduced to their base forms, the parasites will variously try to immediately infect their attacker, withdraw and form a new manifestation for a renewed assault, or flee entirely.

Despite normally being omnivorous, X may ignore potential prey. For example, the Dachoras and Etecoons found in the Habitation Deck, an X-infested area of the BSL station, were left uninfected and were allowed to escape to Samus's ship unhindered, which Adam speculated could be because the X believed them too weak or inferior for use. X may take their time hunting potential prey, as with the Hornoads in Sector 1 and Scisers in Sector 4.

Several Metroids attacking the X Parasites of SR388.

The only known threat to the X are the Metroids, specifically designed for that purpose. Metroids are anathema to the X even on a cellular level, and even the best efforts of the X do little to slow the Metroid's predation. Metroids drove the X population on SR388 to the brink of extinction. However, as soon as the X were accidentally freed from this threat by the actions of the Galactic Federation, they quickly rebounded and retook the planet. In addition, the X creating a form composed of various genetic sources could also in theory be capable of having them kill a Metroid.

With their great versatility, X are able to adapt and thrive in virtually any environment, even those alien to their homeworld. Most dangerously, the X appear to share either a hivemind or a devotion to the welfare of their species, making them willing to go to any lengths, even self-sacrifice, to triumph over their adversaries. In one event, one X attempted to overheat the Station, which not only would 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 and that the sacrifice of the X on board the BSL would have spared their brethren on the planet. Similarly, one SA-X destroys the Restricted Laboratory, which contained their Metroid predators, at the cost of its own life, sparing its brethren on the BSL from the Metroid threat, although this failed as one had escaped. The dire threat they would pose as a galactic plague if able to acquire spaceflight has made their eradication the highest priority any time they are detected.


Before Metroid[]

The Metroids protect the Chozo from nearby X.

The X Parasites evolved beneath the surface of SR388 far in the past, and thankfully were trapped underground, until the Chozo discovered the X while mining for Aeion energy, naming it and learning of its abilities, which horrified them enough to consider it fundamentally "evil".

Recognizing the X's destructive potential, the Chozo created the Metroids in order to keep them at bay.[2][3][4]

In the manga, the Chozo refrained from informing the Galactic Federation of the X Parasites because they accurately feared the Federation would seek to exploit them as a tool.

Metroid: Samus Returns[]

An X Parasite infects a Hornoad in the secret Metroid: Samus Returns ending.

Per the orders of the Federation, Samus wipes out the Metroids on SR388, unknowingly allowing the X Parasites to recover their population, ultimately eradicating all natural life on the planet.[5] They appear in the secret post-credits ending of Metroid: Samus Returns, infecting a Hornoad that was inspecting the Landing Site. They also appear in the game's Chozo Memories.

Metroid Fusion[]

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

Samus's Power Suit infested by X in Fusion.

The Federation first learned of the X on SR388 after 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 emerged from the carcass. The X promptly attached itself to Samus, but it caused no immediate issues and she shrugged it off. However, the X soon infested Samus's central nervous system and caused her to black out while piloting her Gunship, causing a crash that would have killed her if her emergency systems hadn't ejected her. The B.S.L. scientists recovered Samus' escape pod and brought her to Galactic Federation Headquarters for treatment.

They quickly found that Samus was infected by the X and had spread to her Power Suit, forcing them to surgically remove the infected portions. They sent these pieces to the B.S.L. research station for further study, inadvertently allowing them to mutate into the SA-X, but could not fully eliminate the parasites from her body without killing her. 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 vulnerable to freezing temperatures (the primary weakness of the Metroids) and weakening her overall endurance. 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 Starship, and a computerized CO to assist her in her investigations.

Once Samus arrives, she finds the station completely overrun by the X. At numerous points, the X attempt to stop Samus in her tracks by hunting her down, mutating into stronger forms, sealing off or destroying Data Rooms to obstruct her from her upgrades, and even destroying entire sectors of the station in an attempt to take her with them. However, Samus is ultimately able to commandeer the station, sending it on course to impact with SR388 in an immense explosion that destroys the laboratory and wipes out all life on the planet.

Metroid Dread[]

Flashback in Metroid Dread.

Despite their apparent extinction, the Galactic Federation soon learned, via an anonymous video transmission, that some X had survived. The transmission is traced to planet ZDR and a team of E.M.M.I. robots is sent to investigate. When the E.M.M.I. go silent, they reluctantly call in Samus to investigate.[6]

Although the hostile Raven Beak pretends, as part of his act as Adam, to suspect that the footage was staged, Samus eventually discovers that the X are indeed present on ZDR while investigating Raven Beak and the mystery of how the E.M.M.I. went AWOL. When Samus encounters Quiet Robe in Ferenia, the surviving Thoha informs her that one of Raven Beak's Mawkin soldiers was infected during an expedition to SR388, bringing the parasite with it back to ZDR and spreading the disease to the rest of its fellows. Raven Beak contained the X Parasite within the Elun sector, but purposefully releases them after Samus examines the sector. The X quickly spread throughout ZDR and infect all of its organic fauna and Quiet Robe, although they leave mechanical and non-hostile lifeforms unscathed. At one point, the X block thermal energy in Cataris from reaching the rest of ZDR, causing the global temperature to drop, until Samus kills Experiment No. Z-57 and removes the blockage.

Samus eventually defeats Raven Beak and crashes his ship, Itorash. Soon afterward, Raven Beak is infected by an X and turned into Raven Beak X. Upon Raven Beak X's demise, ZDR suddenly begins to self-destruct, resulting in the annihilation of the surviving X species. Many X accost Samus as she runs back to her Gunship in an apparent last-ditch effort to kill her, although they are utterly destroyed by her Metroid Suit and Hyper Beam. Intriguingly, the X copy of Quiet Robe seemingly helps Samus control her Metroid transformation at the cost of its own life and for seemingly no benefit to the X species, allowing her to escape the disintegration of the planet.

Dread reveals that X-infected bioforms that were capable of speech before infection retain the ability to speak. This is demonstrated when Quiet Robe says "I am counting on you..." after being reanimated, and when Raven Beak X says "Samus... Hadar sen olmen"[note 2] when crawling toward Samus. In both cases, the X were repeating some of their host's final words prior to being infected.


The X's sprites were originally reused from the Boyon, albeit colored purple.

The X resemble a species found on Zebes in Super Metroid called Boyon. In beta trailers for Fusion, the X used recolored Boyon sprites.

Base forms[]

Yellow X[]

Yellow X

Yellow X,[7] or yellow parasites,[8] are a basic type of X. When absorbed by Samus, they restore 10 units of Energy in Metroid Fusion and 40 energy in Metroid Dread. 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 host.

Green X[]

Green X

Green X[9][7] appear once Samus regains her Missile Launcher. Like Yellow X, Green X come out of most enemies. When Samus absorbs a Green X, two units of Missile Ammo are restored in Metroid Fusion and 5 Missiles in Metroid Dread.

Red X[]

Red X

Red X,[10] also called red X parasites[11] or red parasites,[8] are usually only released from X-infected Gadora or stronger variations of normal enemies, such as the blue Zeros, although they can also rarely appear from normal enemies. When Samus absorbs them, they restore 500 units of energy, 50 units of Missile Ammo, and 10 units of Power Bomb Ammo (5 Power Bombs in Dread).

Notably, the X that infects Quiet Robe halfway through Metroid Dread is a Red X.

Blue X[]

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 (ブルーのX?), also called Cold X (コールドX?) in Nintendo Official Guide Book for Metroid Fusion, are blue-colored X Parasites that have been changed by the cold in Sector 5 (ARC) of the BSL station. Apparently, the X did this deliberately to both stop Samus from exploring the station and kill her.[12] 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.

When Samus first encounters them in Sector 6 (NOC), 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 Barrier Core-X, she obtains the Varia Suit. When the Varia Suit is acquired, the Blue X can be safely absorbed, restoring 30 units of Energy. Immediately after obtaining the Varia Suit, several unsuspecting Blue X will fly towards Samus in the next room. After a few have been absorbed, the remaining ones will noticeably start to avoid her, and all existing Blue X within the two aforementioned sectors will now flee from Samus as soon as they detect her.

Interestingly enough, they are much larger in size as opposed to the yellow, green and red X, and are unaffected by the Power Bomb's vacuum ability. They are also the only type of X that are never seen taking the form of another creature. The Blue X's more solid nature might be directly caused by its cold characteristics, such as having a more solid/thicker form than other X (logically having its liquid structure being 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.

The Blue X's newfound cold nature in Fusion could have given the X Parasites back on SR388 an advantage against the advanced Metroids initially inhabiting the planet, as the latter can be wounded directly with cold-based weapons (shown in both Metroid: Samus Returns and Metroid Fusion). Although the planet seemingly lacked a naturally occurring cold climate, the Chozo laboratory (initially blocked off by the purple liquid) had snow and ice present within a few rooms. It is unknown if the X Parasites ever reached the lab at some point, nor if the rooms would have been sufficiently cold enough to create Blue X. Dealing with the Larva Metroids would have required additional effort, as the Blue X would be unable to shatter them after encasing them in ice, as they lacked concussive weaponry. On the other hand, mimicking a large, powerful SR388 creature like Arachnus might have given them the firepower to shatter them.

No Blue X appear in Metroid Dread.



Core-X are X Parasites that either carry the DNA of a massive and powerful life form, or have absorbed advanced technological equipment. They protect themselves with a membrane casing that produces regular X Parasites when attacked. When Samus absorbs a Core-X, it restores 400 units of Energy, 50 units of Missile Ammo, and 10 units of Power Bomb Ammo in Fusion, but does not restore anything in Dread.

Orange X[]

Two orange X in Elun.

"Orange X" are a new variant introduced in Metroid Dread. They appear after Samus regains the Power Bomb and restore 3 Power Bombs each.

Purple X[]

Purple X.png

A single "Purple X" only appears once in Metroid Dread, at the very end. It manages to infect Raven Beak after his fight with Samus at Itorash, transforming the Mawkin Chozo leader into a monstrous creature. It also prominently displays features from Kraid, implying that this X had assimilated his DNA as well at some point.

Samus, thanks to her newfound Metroid Suit, manages to dispatch the monster with a well-placed Hyper Beam, doing the same to the Purple X after it reverts to its original parasitic form, obliterating it and leaving no trace of its existence.

Mini X[]

"Mini X" are smaller versions of X parasites that appear in Metroid Dread. They drop from small swarm enemies, such as Dizzeans. Unlike normal X Parasites, they stay where they were killed and cannot appear out of nowhere, change their shape, or fuse with other X. If left alone for long enough, they will simply despawn. They come in Green and Yellow, and appear to reuse the sprites of these colors from Fusion. Green Mini X restore 1 unit of Missile ammo, while yellow Mini X restore 5 units of energy.

Official data[]

Metroid Dread loading screen tips[]

Only Samus can counter the X parasite threat now that their sole predator, the Metroids, have been eliminated. She received this power from the infant Metroid DNA with which she was injected.

The X are parasitic organisms discovered on SR388 that can infect any living creature. They kill their hosts and absorb their DNA to assume the host's form.

An X that has possessed multiple hosts can combine their appearances and traits during the process of replication and morph into a new entity.

The X can even infect dead creatures and assume their forms using DNA absorbed from the corpses.

Other appearances[]

"What's the matter? All I said was that Komaytos look like little Metr-"

Non-canon warning: This article or section contains information that may not be considered an official part of the Metroid series in the overall storyline by Nintendo.

Super Smash Bros. Ultimate[]

X Parasite as a Spirit

In Super Smash Bros. Ultimate, the X Parasite appears as Primary Spirit, which boosts fighters' stats in game modes such as World of Light. It is represented with artwork of three Yellow X clustered together. The X Parasite's type is Attack, which gives it advantage over Grab Spirits but is weak to Shield Spirits, and its class is Advanced. Additionally, upon leveling up the X spirit to Level 99, it can be enhanced into the Nightmare Primary Spirit, which grants the wielder life steal in combat.

The X Parasite can be obtained through the Spirit Board or purchased from Beedle's Tent. In its Spirit Battle, the X Parasite uses Kirby as a Puppet Fighter, most likely since they are both blob-like beings that consume other creatures and copy their abilities. The player must defeat a team of ten Kirby Puppet Fighters appearing in their yellow "Keeby" alternate costume. Each Kirby is more likely to use their Inhale move to copy the player's character. The Spirit Battle takes place on Lylat Cruise, with Sector 1 as the background music.

Non-canon warning: Non-canonical information ends here.


  • 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 on the BSL, nor to re-lock the security hatches that Samus was using. It is also unknown why they disabled the station via Nettori.
  • Strangely, it seems the X cannot directly assimilate or mimic plant life. In Metroid Fusion, the boss Nettori is revealed to be a Torizo controlling vines that are merged with it. When the smaller of these vines are destroyed by Samus’s weapons, or when the larger ones wilt as a result of the boss’s destruction, they do not revert to X parasites. Similarly, the Enky in Metroid Dread, which appear to be a plant or fungus, do not turn into X when destroyed.
  • The fact that the X can infect and imitate their hosts appears to make them similar to the creatures from the science fiction horror film The Thing.
  • The Chozo word for X uttered in Metroid Dread sounds close to Eddis, which closely resembles the Spanish pronunciation of the letter "x", Equis. While the creator of the Chozo language is unknown, this could have been influenced by the developers of Metroid Dread, MercurySteam, who are based in Spain.



  1. ^ This is an approximate transcription; the Chozo name for X Parasites is spoken aloud, but never appears in writing.
  2. ^ Samus Aran's name is pronounced differently in Chozo, sounding more like "Tamus Arlan". However, the spelling remains the same in written Chozo, as seen in the cutscene where the E.M.M.I. are reactivated.


  1. ^ Metroid Fusion manual, pg. 11
  2. ^ Metroid Fusion
  3. ^ Metroid Manga
  4. ^ Metroid: Samus Returns
  5. ^ Yoshio Sakamoto: "I think SR-388's civilization was destroyed and the Chozo left for Zebes after the Metroids were released into the wild (became feral). The Galactic Federation, not knowing the reason why the Metroids were developed, requested Samus to clean them up ("Metroid II"). The result of Samus exterminating the Metroids was that the propagation of the X could permit the SR-388 ecosystem to be destroyed ("Metroid Fusion")." Translated by the Metroid Database. Archived from the original page May 17, 2017.
  6. ^ Metroid Dread Report Volume 5: The Powers of Samus
  7. ^ a b Metroid Prime and Metroid Fusion: Prima's Official Strategy Guide pg. 137
  8. ^ a b Metroid Fusion: The Official Nintendo Player's Guide pg. 15
  9. ^ Metroid Fusion: The Official Nintendo Player's Guide pg. 9
  10. ^ Metroid Prime and Metroid Fusion: Prima's Official Strategy Guide pg. 102
  11. ^ Metroid Fusion: The Official Nintendo Player's Guide pg. 27
  12. ^ 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. Nintendo R&D1. Metroid Fusion. Nintendo. English. 2002-11-17.