Tallon IV

Tallon IV (or Ooromine V) is a Wanderer Class Planet that was impacted by a Leviathan from Phaaze fifty years prior to the arrival of Samus during Metroid Prime. It was inhabited by the Chozo, but after the meteor impact, many left the planet to an unknown destination: all inhabitants who stayed either died out or became corrupted Chozo Ghosts due to the corrupting influence of Phazon.

The Chozo
Tallon IV was chosen to be the dwelling place of a group of Chozo from Elysia who wished to regain their spirituality. Here, they would abandon their technology, instead making their homes out of the planet's resources. This civilization thrived for some time, but they eventually moved beyond the mortal realm. However, it would only be a small amount of time before disaster struck the planet.

The Great Poison
Fifty years before the arrival of Samus Aran, a meteor-like object struck the planet with great force, beginning the planet's downfall. The Chozo were ripped back to the mortal realm due to the meteor's strike. They investigated it, and what they saw terrified them. The meteor had brought with it a terrible poison, which would eventually be named Phazon. The Phazon now spread through the planet, corrupting everything it touched. In addition, the meteor had brought with it The Worm, a horrifying creature of Phazon. The Chozo began to construct a temple in order to contain the Phazon; however, even as they did so, the Phazon gnawed at them, driving many mad. The Artifact Temple was completed, and while the the Phazon spread stopped, the damage was already considerable; the poison had already contaminated a good portion of the planet. The rest of the Chozo wasted away, leaving behind only their ruined civilization and specters of their former selves: those that guarded the keys to the temple were the only ones that remained untainted, while the rest were driven insane by the corruptive power of Phazon.

The Space Pirates
After the events of Metroid, the Space Pirates fled from Zebes. It was only a short amount of time, however, before they discovered massive energy readings emitting from planet Tallon IV. They landed on the planet, and soon discovered the substance known to the Chozo as the Great Poison. Recognizing its immense potential, the Space Pirates named it "Phazon" and began experimenting with it.

They began mining the material, as well. On a mining expedition, however, they accidentally dug through the shield erected by the Artifact Temple...and unwittingly unleashed the Worm: it is possible that the shield only contained the main spread of Phazon coming from the impact crater but not the Worm itself. It attacked the mining team, but it was soon subdued. The Space Pirates began research on it, and discovered that it was incredibly similar to a Metroid genetically. They named it Metroid Prime.

Metroid Prime soon escaped back into the Impact Crater, but not before assimilating some Space Pirate weaponry and making it even more monstrously powerful. It seemed that all hope was lost for the planet.

Samus Aran's Arrival
Unknown to the Space Pirates, Samus Aran had tracked them down, thanks to a distress signal emitted by the Orpheon when its Phazon-corrupted specimens had gone rogue. After exploring the vessel and causing it to crash into the planet, Samus escaped aboard her ship and went down there as well. There, she learned of the downfall of the Chozo, as well as the Space Pirates' experiments. After ruining the Space Pirate research, Samus then brought down the shield containing the Impact Crater and went down there to confront Metroid Prime. After a fierce battle, she was successful. However, in its death throes, Metroid Prime absorbed Samus's Phazon Suit and exploded.

Samus, having ended the threat of Phazon on Tallon IV, left the planet. However, deep within its depths, a new threat was born from the remains of Metroid Prime - Dark Samus.

Tallon Overworld
Main article: Tallon Overworld

The overworld of Tallon IV is mostly lush jungle deluged by constant rain. This is also the area the Space Pirate frigate Orpheon crash landed. Samus landed in this area. Meta Ridley is this area's boss. This is where you enter the Impact Crater. and fight the Metroid Prime.

Chozo Ruins
Main article: Chozo Ruins

Ancient ruins of the once-prosperous civilization of the Chozo. The ruins contain many power-ups and lots of technology left behind by the Chozo. This is the home to the boss creature Flaahgra. The Flaagra once defeated gives you Varia Suit, which lets  you get  to magmoor  caverns.

Magmoor Caverns
Main article: Magmoor Caverns

Underground caverns of Tallon IV, filled with dangerous lava lakes and hostile creatures. It acts as a link between all areas of Tallon IV with the exception of the Impact Crater. It is also the only area of the game that lacks a boss creature. It was named after the creatures that live in the lava in the caverns, Magmoors. The ice spreader can be found here after obtaining the power bomb.

Phendrana Drifts
Main article: Phendrana Drifts

Frozen wastes of Tallon IV's mountaintops. This area contains some Chozo-built constructions and is also the location of the Space Pirate research labs. The boss creature of the area is Thardus. Part of the area has lots of water.

Phazon Mines
Main article: Phazon Mines

The Space Pirate headquarters of Tallon IV. It's where Pirate Phazon ore mining activity takes place and also contains the experimental Elite Pirates and the Omega Pirate, the latter being the boss of the area. The area has elevators leading to all areas (except the Impact Crater, which has no elevators.) The bottom of the Impact Crater can be seen from the level 2 elevator.

Impact Crater
Main article: Impact Crater

Final area of the game, which the player only gains access to after gathering all of the 12 Chozo artifacts and defeating Meta Ridley. The Impact Crater is the heart of the Phazon infestation and contains the final boss of the game: Metroid Prime, a Metroid corrupted by the Leviathan to protect its core. It is accessed from the Artifact temple.

Metroid Prime Scan
Planet Tallon IV Mass: 5.1 trillion teratons.

Profile: Ecosystem studies indicate that Tallon IV was a biological paradise prior to the impact of an extraterrestrial object. What remains of the biosphere is slowly fading due to exposure to Phazon radiation. At current rate of decay, Tallon IV will be a barren Class XIII wasteland in approximately 25 years.

Metroid Prime 3 SkyTown Observatory Scan
Tallon IV appears to be a utopia for biological life, containing an oxygen-rich and hospitable atmosphere. The planet is home to countless species of flora and fauna. Satellite scans detect numerous structures on the planet's surface, with closer examination revealing many of these structures to be of Chozo origin. Tallon IV's scar, the result of a celestial body impacting the planet's surface decades ago, is still visible. Satellite scans are unable to determine the extent of the original damage, but the planet appears to have recovered from any negative effects of the object's impact.

Trivia

 * In Metroid Prime, it is confirmed in the Space Pirate lore scan, "Phazon Analysis", that they discovered a Leviathan had impacted the planet twenty years ago while they were tracing the source of the Phazon there.
 * In Metroid Prime 2: Echoes, Tallon IV can be seen in the background in the multiplayer level Sidehopper Station.