Invasion on Norion

Samus Aran observes a battle between the Federation and Pirates on the surface of Norion.

The invasion on Norion is a full-scale military offensive by the Space Pirates against Base Sector Zero, a Galactic Federation military stronghold on the planet Norion. The Pirates seek to crash a Leviathan Seed under their control onto the planet to begin the process of corrupting it and transforming it into another Phaaze, as they have already begun to do with Bryyo, Elysia and their own Pirate Homeworld. Samus Aran's mission to prevent the Leviathan impact is her first objective in Metroid Prime 3: Corruption. The invasion is named as such by the Lab Assistant that tends to Samus during her month-long recovery following the event.

Background

Space Pirates

A view of Norion.

After a disastrous mission on Aether, during which the Space Pirate mining facility is ravaged by both Samus and Dark Samus, the Space Pirates quickly gather as much leftover Phazon as they can and bring it aboard their battleship, theColossus. However, they also unwittingly collect the molecular remains of Dark Samus, who has been defeated by the real Samus and survived the destruction of Dark Aether. Dark Samus reforms herself by absorbing all Phazon aboard, and proceeds to eliminate a third of the Colossus's crew in minutes, brainwashing the rest to follow her in a quasi-cult.

Dark Samus goes on a months-long journey shortly afterward, and returns with a massive Leviathan. She brings her followers to Phaaze, the origin point of all Phazon, using the Leviathan, and they begin to mechanize the planet for the purposes of accelerating Leviathan production. To achieve this, the Pirates capitalize on an opportunity they learn of from agents within the Galactic Federation. Two months after the Aether mission, the Pirates attack the G.F.S. Valhalla, an Olympus-Class Battleship on a training mission in the Klar Nebula, stealing all Energy Cells aboard, but more importantly, its Aurora Unit: 313.

Returning to Phaaze, the Pirates corrupt 313 and establish a symbiotic link between the Aurora Unit and the planet. This allows Dark Samus to create and send Leviathans to planets at her will. She first sends a Leviathan to the Pirate Homeworld, providing the Space Pirates there an organism rich in Phazon, which they can use to build a massive army. However, Aurora Unit 217 on SkyTown, Elysia detects the impact and traces its origins to the planet Phaaze. Before it can report its findings, Dark Samus sends a corruption virus through the entire Aurora Unit network via 313, forcing the Federation to disable it.

Once more Leviathans have matured, Dark Samus launches them at all three planets in the Federation Solar System: Bryyo, Elysia, and Norion. Those sent to the former two planets impact successfully, while the seed intended for Norion is sent last. Norion will be the most difficult target, as it is the home base of the Federation Fleet. Dark Samus and Meta Ridley are both present on Norion to oversee the impact.

Galactic Federation

The Galactic Federation is able to quickly devise a vaccine to cure the Aurora Units of the corruption virus before they would be unable to reverse the damage. While most of the units have been cured, a few remain infected, and the Federation hires Bounty Hunters to deliver the Galactic Federation vaccine to these units.

Fleet Admiral Castor Dane summons four hunters to the G.F.S. Olympus Ready Room - Samus Aran, Rundas, Ghor, and Gandrayda - and assigns them with delivering the vaccine to the remaining AUs. He notes that with the network offline, the Federation is vulnerable to attack. Almost by chance, Aurora Unit 242 proclaims a condition red, as a Space Pirate attack on Base Sector Zero is detected. Dane realizes that they are targeting the planetary-defense system, and orders the four hunters to assist the ground troops in repelling the attack.

Attack

Samus fights a Pirate Aerotrooper on Cargo Dock A.

Landing on Docking Hub Alpha, Samus is alerted to the invasion by a Federation Marine, who informs her that the Pirates have disabled the three Fedtech Plasma Generators that power the planetary Defense Cannon. Samus rushes to reactivateGenerator A and Generator C, battling hordes of Space Pirates along the way, while Rundas reactivates Generator B for her.

While exploring, Samus witnesses Meta Ridley flying over the base, and is later trapped by him in a Morph Ball tunnel.

In Generator C, Samus witnesses Gandrayda impersonating Pirate Militia, before flirtatiously leaving Samus to reactivate the generator, as "machines aren't my thing". As she is reactivating Generator C, Ridley ambushes her and sends the both of them falling down an exhaust shaft. Samus defeats Meta Ridley before falling to the bottom, and is rescued by Rundas, who leaves her to reactivate Generator C.

After Generator C is reactivated, Samus is alerted to the oncoming Leviathan by Dane. With no time to lose, Samus rushes to the Control Tower, barely making it to meet the hunters. At the top, they begin the process of restoring the Defense Cannon, when Dark Samus appears through the window. She proceeds to unleash a massive blast of Phazon toward the four hunters, grievously wounding them. Samus uses the last ounce of her strength to fully activate the Defense Cannon before losing consciousness.

Aftermath

Rundas, Ghor, and Gandrayda awaken from their comas within a few weeks, while it takes Samus an entire month to awaken from hers. The Galactic Federation discovers that as a result of Dark Samus's attack, the four hunters were now self-generating Phazon within their bodies. This corruption is initially assumed to be benign, and they take advantage of this by installing Phazon Enhancement Devices onto the hunters so that they can exploit their Phazon. Samus awakens to find that the Federation has created the PED Suit by installing the PED into her Chozo armor.

Upon meeting with Aurora Unit 242, Samus learns that Rundas, Ghor, and Gandrayda have been sent to investigate the Leviathan Seeds on Bryyo, Elysia, and the Pirate Homeworld, but contact with all of them has been lost. Samus is assigned with finishing their missions and destroying each Leviathan Seed. She discovers that their corruption is actually a slow-acting poison: remaining in Hypermode, a state of power that Samus achieves by tapping into her Phazon, for too long can cause her to succumb to Terminal Corruption, and fall under Dark Samus's control. Samus discovers that this is the fate of the other hunters, and is forced to defeat each of them.

Although Norion is spared a devastating end, it will be some time before it fully recovers from the assault. One month after the invasion, maintenance is seen to still be underway. The entirety of the sector leading to Generator B is still overrun by spent Phazon, where none of the troopers are willing to enter. Many rooms that Samus has entered previously are now blocked by Marines due to repairs. Samus can enter Generator B and defeat a Metroid Hatcher to obtain Energy Cell ID: WI-7823I-3.

Eventually, Samus ventures to Phaaze and confronts Dark Samus and Aurora Unit 313 for the final time, destroying both them, and Phazon once and for all.