Leviathans are enormous alien creatures that appear in Metroid Prime 3: Corruption. Described as "living meteors", these entities are the offspring of the living planet Phaaze and exist solely to spread the mutagenic substance known as Phazon to other planets across the universe, corrupting those worlds and transforming them into Phazon planets similar to Phaaze itself.
Life Cycle Edit
Leviathans are the "children" of Phaaze. Born in a serpentine womb deep within the planet, they feed on vast amounts of Phazon energy until they develop a Phazon Core, which marks their transition into adolescence.
Before this, they are extremely unstable, though naturally extremely resistant, and cause massive explosions if damaged before full maturity. Once they reach adolescence, the Leviathans are slowly pushed upward to the surface until they mature to their adult size. The oldest Leviathans are up closest to the surface while the youngest are below. As Leviathans are launched into space, the younger ones move closer and closer to the surface. As mentioned above, an unspecified number of these creatures are launched every 100 years; the reason behind this century-long wait is likely the required time for infants to reach full maturity. Finally, once Phaaze has found a planet to corrupt, it launches the Leviathan into space, in hopes of impacting a planet.
After ejecting from Phaaze, the Leviathan will create a wormhole to shorten its journey to the intended planet. The Leviathan will home onto its closest target and impact the planet, spreading Phazon from the collision. The strength of this collision has been known to vary greatly, sometimes leaving huge scars upon the surface of the impacted planet. After collision, the Leviathan's Phazon Core, which it developed at the end of its infant stage, slowly seeps its way into the planet, spreading corruption and replacing the ecosystem with one that is Phazon-based. At this point, the Leviathan may possibly attract a native creature and corrupt it with massive amounts of Phazon. The corrupted creature serves as the Leviathan's guardian, to protect its Phazon Core. Some time after this, the Leviathan itself will die, leaving behind the "husk" of its body which will serve as armor to protect the core's environment against attacks from the outside.
Leviathans are a silicon/Phazon-based bioform in that, at full maturity, appear to be made of a rocky substance which is likely why information pertaining to them refers to them as meteors. They are covered with large patches of Phazon and have long tentacles growing out of their sides. The inside of a Leviathan appears similar to a cave containing various Phazon-based life and Phazon-generating organs. The passages that lead to the core chamber of the Leviathan appear as transparent tubes, similar to veins, but without liquid within them. There are doors in the Leviathan that seem to be a type of sphincter valve with a weak energy field covering it. The core chamber is a large spherical room, with many pulsating and moving objects which may be organs. The Phazon Core itself resides at the top of the chamber in a sealed sac-like sheath. The Core's appearance is that of a large, round, insectoid creature connected to the ceiling by several cords that it moves around with. It is covered in Phazon growths, has several eyes and a mandible-like mouth. The chamber is also usually where the Leviathan's guardian resides. Because the Leviathans on Tallon IV and Aether were not expressly shown, it is difficult to say which attributes of the three featured in Corruption are characteristics of immature Leviathans and which ones apply to all.
Impacted Planets Edit
Fifty years prior to the first Metroid Prime, a Leviathan impacted Tallon IV and brought Phazon to the planet. Upon impact, the Leviathan acquired a Metroid to serve as its guardian (it would later be named Metroid Prime by the Space Pirates,) that was the Leviathan's Guardian and was feeding on the seed's Phazon. Several days after its impact, the Chozo residents of Tallon IV were able to greatly slow down, if not completely stop the spread of Phazon on the planet by building a temple named the Cradle, which used an unseen containment field. This particular Leviathan seems to have many characteristics that differ from its brethren, such as having a higher lethality rate towards local populations than seen on the Pirate Homeworld. This suggests that the molecular composition of the Phazon brought to Tallon IV, and possibly also that which was brought to Aether, were from fully matured Leviathans compared to the ones seen in Metroid Prime 3: Corruption, as Dark Samus (a.k.a, Metroid Prime) would have no doubt been impatient to wait 100 years for them to grow and thus launched them prematurely during her reign. The Impact Crater was likely the Leviathan for Tallon IV, but since there was no visible sign of the Leviathan itself in the game, it can be speculated that the creature was consumed by its Guardian, Metroid Prime, due to the creature's insatiable hunger for Phazon (a common trait in Metroids), just as it is assumed that Prime also absorbed the seed's Phazon Core, giving it the ability to produce Phazon. This might explain why the hypertoxic substance found in the Impact Crater was not encountered on Phaaze: It may have been produced by the instability and/or decay of the Leviathan's body, the Phazon Core or the surrounding environment, namely the additional pressure present in the Crater due to the Cradle's containment field, which may have concentrated the Blue Phazon into Red Phazon. Alternatively, since Samus teleports directly into the Impact Crater, it is logical to suggest that the Leviathan does in fact continue to exist in its entirety; the Artifact Temple is likely built over it and the crater in order to contain it, thus no outside view of it can be seen. However, the Artifact Temple itself somewhat resembles a greatly aged Leviathan husk, with the Chozo structures built on it. Looking through a glass window in one of the elevators that leads towards the Phazon Mines shows the weathered temple/Leviathan floating above the crater.
About the same time as a Leviathan hit Tallon IV, a Leviathan impacted planet Aether, visited in Metroid Prime 2: Echoes. However, due to the instability of Aether's planetary energy, another dimension, known as Dark Aether, was ripped open; the Leviathan itself, along with nearly all of its Phazon, was teleported to Dark Aether at the moment of impact. This Leviathan was also never seen in-game. The Emperor Ing may have possibly served as the guardian of the Aether Leviathan Core, and the large quantities of Phazon in the Sky Temple Gateway might suggest that the Aether Leviathan impacted nearby.
Several months after the events of Metroid Prime 2: Echoes, a Leviathan impacted the Space Pirate Homeworld. This was the first one to be controlled by Dark Samus. Ridley would later be chosen as its guardian, soon to be named Omega Ridley.
A few months after that, Dark Samus sent three more Leviathans to corrupt a number of planets. They were headed to Norion, Bryyo, and Elysia. The one aimed for Norion was destroyed before impact, but the ones headed to Bryyo and Elysia were unharmed until Samus Aran destroyed the Phazon Cores within them. The Bryyo Leviathan's guardian was a corrupted Mogenar War Golem, while the Elysia Leviathan's was a massive mechanism called Helios. Interesting to note is the fact that the first Leviathan seen in Metroid Prime 3: Corruption was easily destroyed by Federation tech, while Luminoth and possibly Chozo technology, were unable to destroy their respective Leviathans at all. This is considered strange as both mentioned species are highly evolved sentient creatures whose technologies far surpass the Federation's. This leads to the mentioned theory that the Leviathans launched prior to Dark Samus' control over Phaaze were at the peak of their growth, possibly having a stronger surface. Though in case of the Chozo on Tallon IV, it may have simply been due to the fact that the Chozo of that planet chose to build a colony from natural materials and so lacked the technology needed to destroy the Leviathan. It is also mentioned that the Chozo were, before impact, ascending to another dimension, leaving their physical bodies waiting for their consciousness to return; they were violently pulled back to the physical realm at the time of impact. In the case of the Luminoth, no piece of information is given other than a lore that described them using various weapons against the coming Leviathan before impact, with no avail. They could do nothing but wait for the inevitable. Careful inspection of a Leviathan reveals it to contain more bulk on its front than the rest of its body; this leads to another explanation that the Federation were able to destroy Norion's respective Leviathan by attacking its side which is seemingly less armored than its front (it is logically plausible that the front is heavily resilient to resist collision with a planet and deliver its Phazon cargo intact).