The X-Parasites is a type of extremely dangerous parasitic creatures native to the planet SR388. They were the apex predator of the planet with the ability to infect and kill anything organic very quickly. They are not simple parasite, however, their parasitic nature is a mean for them to copy the genetic material of their victim, which then allows them to transform into replicas of these creatures. The danger this represented was what motivated the Chozo to create the Metroid, a type of artificial creatures with a genetic sequence made to directly eliminate the X-Parasite. The parasite's presence was greatly reduced on SR388, and they only began to thrive once more after Samus Aran destroyed all the Metroids on the planet.

The mind of the X-Parasite is never explored in much details but it is said that they also absorb the knowledge of their prey and thus became very intelligent after absorbing an entire station filled with human personel. They seem to also share some sort of hive mind and are depicted with the ability to anticipate Samus' actions and even mess with the station's computers after having gained more knowledge. They serve as the main antagonistic force during Metroid Fusion. During that game they take on the appearance of various creatures the X-Parasite has infected in the past, including the terrifying SA-X.


The X-Parasite is similar to a bowlingball sized viral life form in its appearance and mode of predation. Unlike most viruses, the X-Parasite is enormous but like them it messes with their prey's genetic code in order to further spread themselves to new hosts. The regular X-Parasite looks like a floating gelatinous blob that varries in color depending on its function. They can simply infect a new host by coming into contact with them. The X-Parasites also have an evolved form called the Core-X. The Core-X is an individual X-Parasite that gained a new ability upon assimilating a strong host. The Core-X will take on a form that ressemble a virus even more. They now have an external membrane with spikes coming out of it. The Core-X can also produce new offsprings without infecting new hosts, which contributes to the species' rapid spread. They often take on the form of the host that gave them their new ability to fight any threats to their survival. Every boss in Fusion except the final boss is a Core-X that has assimilated an extemely dangerous life form and uses its likeness against Samus. The X-Parasite also has the ability to quickly mutate to adapt to their environment. This happens during Fusion as a bunch of X-Parasite that purposefully infiltrated the artic section of the space station quickly mutated into icy variants of the X-Parasite to take advantage of Samus' newfound ice weakness.

The X-Parasites cannot be harmed by normal weapons since their body is gelatinous, beams and physical projectiles go right through them. The only exceptions being the Blue X whose body harbor large quantity of ice making them more solid than the usual X-Parasite. This means that they can be stunned by projectiles, they still don't damage their body however. The Core-X's membrane is also solid, which means that it can be broken to expose its core. The only real weakness the X-Parasite has is the genetic structure of a Metroid, which was designed specifically to shut down any X-Parasite trying to prey on a Metroid. The Metroids are the only predator of the X-Parasite and after Samus's DNA is spliced with Metroid DNA, she gains the ability to feed on the X but gains the Metroids' weakness to ice.

Types of X-Parasites

Yellow X


The Yellow X is the basic type of X-Parasite, they are the ones depicted in most artworks. The X-Parasite that infected Samus on SR388 was a Yellow X. They are the most common type of X-Parasite. They will restore 10 units of energy if Samus absorb them after defeating their host.

Green X


The Green X is a slightly rarer form of the X-Parasite. They only start appearing after Samus restores her Missile Launcher upgrade. The Green X are also very common comparatively to other types of X-Parasites. They will restore 2 Missile if Samus absorbs them after defeating their host.

Red X


The Red X is a rare type of X-Parasites. They are notably stronger than the other X-Parasites and usually take on the form of stronger hosts as a result. They can mostly be found mimicking Gadoras or stronger variants of standard enemies. They can also rarely appear when normal enemies are defeated. They will restore 500 units of energy, 50 missiles, and 10 Power Bombs if Samus absorbs them after defeating their host.

Blue X


The Blue X is a mutated variant of the X-Parasite that can only be found in icy areas and the zones next to them. This could mean that they are the rarest type of X-Parasite on the station but they seem to have multiplied quite fast and a great number of them can be encountered in the artic habitat. They don't even try to mimic a host. Their goal is to be willingly killed by Samus. The reasoning behind this is that since she needs to absorb them to kill them, they can take that opportunity to fill her system with the ice stored inside their body. This reacts negatively with her Metroid DNA and harms her a lot. As a result, the Blue X will try to enter Samus body by force as soon as they see her. They do start to run away once they realize that she has obtained the Varia Suit. They are much larger than the other X-Parasites in size and can be stunned with projectiles. The will restore 30 energy units if absorbed after obtaining the Varia Suit.


Early History

The Chozo discover the X-Parasite

The X-Parasite are a lifeform that evolved on the planet SR388. They eventually became the apex predator of the planet as no organism native to it could successfully hunt the X-Parasite, while they could prey on all of them. Eventually, the Chozo started to colonize SR388 and encountered the X-Parasite. They were the ones to name the X-Parasite and quickly discovered the terrifying abilities of the X. They deemed it an "evil" to defeat and to do so they examinated their genetic material and created artificial beings acclimated to SR388 with the ability to prey on the X-Parasite and a genetic sequence that would make them immune to any infection. The Metroids were thus created. These events are depicted in the Metroid Zero Mission manga and in the Chozo Lore, which was featured in Metroid: Samus Returns. The manga explicitely state that the Chozo refrain from telling the Galactic Federation about the X-Parasite's existence out of fear that they would try to weaponize it, which happens in Fusion.

The Metroids are used to hunt down the X-Parasite.

Soon after creating the Metroids, they mutated due to the environment found on SR388 and the Chozo are pushed back out of their colony. The Chozo decide to seal the Metroids within the planet and ask for help from an unknown Chozo group. Upon their arrival this group turns on the Chozo elders and murder any survivors from the planet after they are told what is happening by one of the elder. The warring Chozos then leave the planet, which remains as a Metroid dominated world until Samus shows up. The X-Parasite is clearly still alive after the Metroids take over the planet so it is almost guaranteed that they continued to exist in small pockets away from their predator while they were dominating the SR388 ecosystem.

The Metroid Genocide

The X-Parasite returns after the defeat of the Queen Metroid.

Prior to the events of Metroid: Zero Mission, the Space Pirates under the command of the rogue Chozo A.I., Mother Brain, launched an expedition to SR388 where they captured a few Metroids. The Metroids were brought back to Zebes where Mother Brain started a breeding program to eventually use them as weapons. After Samus defeated Mother Brain for the first time, a Galactic Federation expedition was sent to SR388 to investigate the Metroids. After this squad went missing, Samus herself was sent on the planet with the task of eliminating the Metroid menace. Samus killed every Metroid she encountered and used their DNA as proof that the Chozo seals could be removed safely to allow her to continue her rampage further. She eventually reached the depths of the planet where she fought and eliminated the Queen Metroid. She took with her the last remaining infant Metroid, that she named The Baby, and went back to the Galactic Federation to give it to scientists there. Soon after the Metroid genocide was completed, Samus Return shows that the X-Parasite pockets that were isolated were allowed to multiply once again. The final scene of that game depicts a X-Parasite possessing a Horntoad, which symbolize their return to the role of apex predator of the SR388 ecosystem.

The Biologic Space Laboratories research station incident

Samus is infected by the X

Following the second defeat of Mother Brain and the destruction of Zebes, Samus returned to SR388 in partnership with the Galactic Federation's "Biologic's research team" to capture native life forms to store and study in their Biologic Space Laboratories research station orbiting SR388. During the expedition, Samus is infected by the X-Parasite after defeating a Horntoad host. The X doesn't manifest immediatly in Samus. It does when she is flying back to the Biologic Space Laboratories, which cause her to fall unconscious and crash her ship in an asteroid belt. Samus was ejected in an escape pod and quickly recovered by the scientist team found nearby. They realize Samus' condition but are unable to operate on her since her suit is partially organic, linked to her neural system, and cannot be removed when the user is unconscious. They are forced to take it appart by force and inject the dying Samus with a vaccine made from Metroid DNA samples taken from The Baby. Samus becomes part Metroid as a result and gain the ability to absorb the X-Parasite as well as a weakness to ice. What remains of her suit undergo a transformation as a result and becomes the Fusion Suit. Thee infected pieces of her Power Suit are sent alongside the new SR388 specimen in the Quarantine Bay of the Biologic Space Laboratories research station for further analysis.

The SA-X

This turns out to be a mistake as the X-Parasites in the remains of the Power Suit begins to mimic Samus since she was their host for a while. This creates the SA-X, which has stolen most of Samus' abilities while it was infecting her. With its newfound intelligence and power, the SA-X escape the quarantine Bay and begin to spread across the B.S.L. research station. Most of the personel is quickly killed or assimilated and the SA-X produce more X-Parasite to infect the animals that were held in captivity aboard the station. Samus is dispatched with a computer version of Adam Malkovich after an explosion is detected aboard the station since she is the only one immune to the X-Parasite.

Upon her arrival, the duo confirms pretty quickly that the breach of containment in the Quarantine Bay was caused by the X-Parasite as she encounters a few of them mimicking Horntoads in the hallways of the station around the bay. Soon after she defeats a Core-X and realize that the X have taken her abilities and that she needs to defeat more to get them back. The X-Parasite manages to break into Sector 1, which is a replica of the SR388 ecosystem. While Samus isgoing there on an elevator, SA-X is shown for the first time to the player. Samus and Adam try to contain and destroy the X but they seem to be able to outsmart them at every turn and take advantage of their plans to spread to other sectors. Adam suspects that someone intelligent is helping the X and after reaching the other sectors, Adam confirms that he has isolated that supposed helper and that it is an X immitation of Samus at full power. From that point on Samus is hunted by the SA-X who is way stronger than she is at the moment and take advantage of her Ice Beam and ice weakness to deal massive damage to her. Samus is able to gradually recover her powers by killing more Core-X and avoiding the SA-X. After the X-Parasite is shown purposefully staying in an artic environment to mutate into the Blue X and exploit's Samus' weakness to ice, Adam really begins to question their level of intelligence. Soon after, it is revealed that the X had been mimicing humans researchers and had purposefully shut off the main boiler of the station in an effort to kill Samus and the X on board. Adam question why a such a creature would go against their instinct of survival and then comes to the conclusion that their newly birthed intelligence deduced that killing Samus in a suicide attack would be better in the long run for their species as she could eventually hunt down the remaining specimens found on SR388.

Eventually, it is revealed that the Galactic Federation and Adam have ulterior motives and the support sent to Samus begins to dwindle as she hunts the X more efficiently. She eventually disobey orders and enter a classified zone of the station where she realize that the Federation had been cloning Metroids in secret. She is soon attacked by the SA-X but this backfires as the Metroids are freed in the commotion and they immediatly go after the SA-X since they were designed to kill X-Parasites. Samus initiate a self destruct command and the secret lab is detached from the station and fall from orbit on SR388 with the Metroids and the SA-X on it thus destroying both. Adam immediatly contact Samus and tell her that she disobeyed order and that she will have to pay a price for that. He then reveal that there are no less than 10 SA-X on the station as they have been multiplying and that the one who died is irrelevant to the Federation's greater plan. He then seal the entrances of the room she is in and tell her that the Federation is planning on capturing the remaining SA-X and turn them into weapons. Samus protest and is able to convince him to betray the Federation by making him remember his past life as a human. The duo decide activate the self destruct mechanism of the station.

The SA-X tries to kill the Omega Metroid.

On her way there, Samus is ambushed by one of the SA-X and defeats it but it's X-Core flies away. Once she activates it a timer starts to count down and she goes straight to her ship but on the way she run past membranes that have been shed by an unknown organism. Once she reach her ship she comes to the horrible realization that the membranes she saw were from a Metroid that escaped the secret lab in the chaos of the SA-X attack. She is ambushed by an Omega Metroid that was able to reach that stage due to the fact that the station recreate SR388's environment. Samus tries to take on the beast but is unable to without her ice beam. The second SA-X then reappears and try to kill the Omega Metroid with the Ice Beam. It is easily knocked in its Core-X form by the predator at which point Samus seize that opportunity to fuse back with the upgrades the SA-X stole and regain her Ice Beam. With it, she finishes off the Omega Metroid and escape the exploding station.

ZDR incident

Prior to the events of Metroid Dread, a video transmission from an unknown source is sent to the Galactic Federation, informing them that the X have survived their previous encounter with Samus. The transmission is traced to the planet ZDR, and a team of E.M.M.I. research robots is sent to investigate. Samus, now presumably wanted by the Federation for her disobedience of their orders, somehow intercepts the message and travels to ZDR to find out if the X truly are alive.

After Samus goes to Elun she founds out tha the X are alive, after figthing an X infected Chozo Soldier, the X are released from Elun and invade the entire planet.

Super Smash Bros.

Super Smash Bros. Ultimate

The X-Parasite is featured as a novice primary Spirit in Super Smash Bros. Ultimate.

No. Image Name Type Class Slots Stats Ability Acquisition
X Parasite.png
X Parasite Attack 2
  • 948—4,748
  • Brawn Badge: 341—1,709
  • Protection Badge: 607—3,039
Can Be Enhanced at Lv. 99
  • Purchase at Beedle's Tent for 500SP
  • Battle via Spirit Board