Phaaze

Phaaze is the final location Samus Aran visits in Metroid Prime 3: Corruption, and the entire Metroid Prime trilogy. It is the source of all Phazon. From Phaaze, the Leviathans are grown and sent into space to corrupt planets, such as Tallon IV, Aether, Norion, Bryyo, Elysia, and the Space Pirate Homeworld.

Features and History
Phaaze is a living planet. Within the planet is a womb where Leviathans are born and grown. Once they mature, they leave Phaaze and corrupt planets with Phazon. As the Leviathan corrupts the planet, it takes control of a powerful local bioform and corrupts it to protect its core. The planet is completely composed of Phazon. This may mean that there could be undiscovered strains of Phazon. The existence of Black Phazon Crystals was previously unknown until discovery of the planet. The planet has entire seas of blue Phazon and continents formed of a previously unknown type of green Phazon, although there is no orange Phazon to be seen.

Phaaze was first discovered by a Chozo Searcher on Elysia. A once-thought-lost probe began transmitting data on Phaaze. However, this data only revealed minor details about the planet. The Chozo Searcher learned that Phaaze was somehow "alive". Seeing as how the Leviathans (living meteors) are produced in caverns with structures that resemble wombs, Phaaze could very well be a living creature. Unfortunately, the data being collected was lost before the Chozo could analyze it. Further research about the planet was next to impossible, as Phaaze was incredibly far away, even for Chozo space-travel standards. After this, Phaaze would be undetected for many years. The next time that bioforms exotic to Phaaze would lay eyes on it would be when Dark Samus brought the Space Pirates there. Following the Space Pirate attack on the G.F.S. Valhalla, Dark Samus implanted Aurora Unit 313 into the planet itself, allowing her to control the planet and its resources.

Finally, the Galactic Federation tracked the origin of the Leviathans to Phaaze. They began preparing to travel there to put an end to Phazon's destructive power. After taking control of a Leviathan and warping there, the Federation engaged the Space Pirate fleet in orbit above the planet while Samus headed down there to find Dark Samus.

After traveling through Phaaze's depths, Samus confronts Dark Samus. After they do battle, Dark Samus calls forth Aurora Unit 313 and merges with it. Samus destroys the corrupted Aurora Unit that is connected to Phaaze. Due to the symbiotic nature of this relationship, the destruction of the Aurora Unit causes a chain reaction that culminates in the destruction of both Dark Samus and Planet Phaaze itself. As a result, all Phazon is destroyed.

Biology
All life on Phaaze is Phazon-based. Phazon Metroids and Hopping Metroids are abundant, as well as Phazon Puffers, Phazon Hoppers, and Phaz-Ing. In addition to this, many previously unseen bioforms inhabit Phaaze. An infant Leviathan can be found on the planet, as well.

Husks of bioforms similar to Metroid Prime can also be found behind the Leviathan womb in the Genesis Chamber, though it is unknown if these are peeled/molted skin left by the Metroid Prime that reached Tallon IV or if they belonged to other Primes living on Phaaze. It is likely that the Phazon-rich environment caused a Metroid/Hopping Metroid on the living planet to mutate into this heavily evolved form.

Dark Samus also appears on Phaaze, as it is her base of operation, as well as being her homeworld and can absorb energy from the planet itself to heal herself in battle. Aurora Unit 313 has been implanted into the planet's core.

Samus's Arrival
Seconds after arriving on Phaaze, Samus' Phazon corruption reaches nearly critical levels, causing her to remain in hypermode permanently. Samus becomes so corrupted (though not completely, as she still retained her free will) that her gunship no longer recognizes her as Samus Aran, therefore denying her access to her ship for the rest of the game.

Also, all energy tanks are "vented", and a yellow bar at the top of the H.U.D. is there in its place. As Samus is exposed to Phaaze's atmosphere, this bar will gradually fill. Taking damage also fills the meter. The bar will deplete when units of "Anti Phazon" are absorbed, or when using the Hyper Grapple to expel energy/Phazon into an enemy. When the meter is maximized, Samus becomes fully corrupted, and the game is over, showing a disturbing new sequence where Samus, from the Phazon corruption, turns into a new Dark Samus.

Bosses

 * Dark Samus
 * Aurora Unit 313

Etymology
A phase is one part or portion in recurring or serial activities or occurrences logically connected within a greater process, often resulting in an output or a change.

Trivia

 * The destruction of Phaaze due to the defeat of Aurora Unit 313 is very similar to the destruction of Zebes after Mother Brain is destroyed by Samus in Super Metroid.