Fission Metroids are mutated Metroids, created from either Tallon Metroids being exposed to the mutagen known as Phazon, or born directly out of pools of said mutagen. These organisms have the ability to split into two similarly mutated Metroids. They are only featured in Metroid Prime.


A pre-division Fission Metroid in the Impact Crater.

Structurally, Fission Metroids are identical to their common counterparts, with a translucent, veined membrane housing four nuclei, and two pairs of curved mandibles on its underside for simultaneously latching onto prey and absorbing its energy. However, a pre-division Fission Metroid can be distinguished by its colorless membrane, aqua-tinted nuclei and translucent mandibles.

After sustaining enough damage from any weapon, a Fission Metroid will divide into two randomly-colored duplicates, each with a newfound immunity to 92% of Samus Aran's arsenal. However, due to the unstable nature of this mitosis, these new Metroids are susceptible to a single Beam weapon and its Combo, which can be determined by the color of its membrane and nuclei. In addition to their colorless "parent", there are four possible types:

All Fission Metroids are also vulnerable to Bombs and Power Bombs, the latter of which can destroy them instantly.


In the NTSC version of Metroid Prime, Fission Metroids are found exclusively in two rooms within the Impact Crater, notably in the Phazon Core room where they are infinitely spawned from Red Phazon bubbles; their constant presence and abilities make them an obstacle to overcome when climbing the vertical room. The quickest method of dealing with the creatures requires use of the limited amount of Power Bombs, which can kill Fission Metroids without triggering a split. The organisms make their second appearance when Samus Aran fights the Metroid Prime's core essence in its lair; the creature can spawn Fission Metroids from the pools of pure blue Phazon it creates, but only after normal and Hunter Metroids were spawned earlier in battle. At this particular point in the game, Samus can access the devastating Phazon Beam, the only other weapon capable of killing Fission Metroids instantly. These organisms, along with the Metroid Prime, are the first in the Metroid series' chronology to have gained invulnerability to their species' common weakness: cold temperatures. Years later, the Galactic Federation would successfully recreate this invulnerability in the Unfreezable Metroids located on the BOTTLE SHIP.

In all subsequent versions of the game, such as the PAL version of Metroid Prime, New Play Control! Metroid Prime and Metroid Prime Trilogy, a weaker variant of Fission Metroids begins appearing on the third floor of the Phazon Mines after the death of the Omega Pirate. They can perish if they come into contact with nearby Phazon growths, get hit by an Auto Defense Turret's projectile or approach the Red Door leading to the Processing Center Access room. They can also die from a few shots of Samus' weapons before having the opportunity to divide. The differences in strength between the standard and frail Fission Metroids may be attributed to the types of Phazon present in the areas they are located in. Both variants can explode if they overfeed.

Official data[]


"Fission Metroids are mutant Metroids with the ability to split into two forms. This split endows the new creatures with invulnerability to most weaponry. This effect is unstable, though, so during the split the Fission Metroid remains vulnerable to one particular type of weapon fire. The vulnerability appears to be random, perhaps due to the chaotic nature of Phazon mutation.

An energy-based life-form with a translucent upper body. Claw-like spikes protrude from the lower half of the creature, which it uses to latch onto its prey."

Logbook entry[]

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Fission Metroid scanpic.png

Fission Metroid

Metroid Prime

Temporary scan

Morphology: Fission Metroid
Metroid with the ability to split into two forms.

Logbook entry

The Fission Metroid is a mutant, capable of splitting in two. This split endows the new creatures with invulnerability to most weaponry. This effect is unstable, resulting in weakness to a type of weapon fire. The vulnerability appears to be random, due to the chaotic nature of Phazon mutation.


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  • The images erroneously used for the Fission Metroid on are that of a Hunter Metroid.
  • Visually, the manner in which a Fission Metroid divides is identical to a natural Metroid larva multiplying after being exposed to Beta-Rays. Both processes are akin to a cell undergoing mitosis.
    • Phazon has demonstrated the capacity of being able to multiply/spawn Metroids in various ways throughout the Metroid Prime series, an example being the Fission Metroids. The only other substance known to be capable of unnaturally increasing a Metroid population is Beta-Radiation. Whether this means that both substances emit similar energy signatures is unknown.
    • While Tallon and Hunter Metroids can be produced from blue Phazon in the Impact Crater, Fission Metroids are the only ones able to be birthed by both blue and red Phazon in the same area. The fact that the Metroid Prime is stated to be the source of Phazon on Tallon IV may imply that the mutagen it creates carries its genetic information, thus allowing Metroids to be born out of the substance.
  • Due to their infinite spawning from non-destructible bubbling portions of Red Phazon in the Impact Crater, the Fission Metroids can be viewed as "pipe" enemies seen in both 2-D and 3-D games in the Metroid series, such as Zebbos and Plated Puffers.
  • The red Fission Metroids bear a slight resemblance to the Red Metroid variant from the original Metroid game.
  • The red, purple, and yellow variants could be classified as Unfreezable Metroids as they lack the species' vulnerability to the Ice Beam. The white variant inherits this vunerability.
  • Fission Metroids will not chase Samus if she enters another room. They are seen patiently waiting for her to return into the Phazon Core room. If a Metroid latches onto her and she passes through an open door, the Metroid will instantly explode.
  • Unlike the Fission Metroids spawned from Metroid Prime itself, the Fission Metroids encountered within the Phazon Core cannot be immediately destroyed by the Phazon Beam (seen via hacking). After a few shots from said beam, the Fission Metroid will split. Its split selves are highly vulnerable to the Phazon Beam as well, killing it within seconds.