Story
After illegally landing on Rubicon 3, C4-621 steals the license of a deceased mercenary and assumes their call sign: "Raven". With the new identity, Raven inserts themselves into the war raging on Rubicon's surface between the megacorporations Balam Industries and Arquebus Corp, the anti-corporation Rubicon Liberation Front (RLF), and the Planetary Closure Administration (PCA), who are all racing to find or protect the Coral. During numerous battles, Raven ends up befriending V.IV Rusty, an elite AC pilot working for Arquebus's Vespers unit; "Cinder" Carla, leader of RaD, an organization of black-market arms dealers; and G1 Michigan, the leader of Balam's Redgun unit, who treats Raven as an honorary member. They occasionally provide assistance directly or through comms. In addition, Raven encounters G5 Iguazu, a Redgun AC pilot who envies Raven's exploits and develops a one-sided rivalry with them; and V.II Snail, the leader of Arquebus's Vespers, who looks down on Raven due to Raven's supposed inferior augmentations.
At Walter's bidding, Raven destroys a PCA "Watchpoint" used to monitor Coral, but is unexpectedly caught in a Coral surge. This causes them to make telepathic "Contact" with a Rubiconian named Ayre, who helps Raven escape alive. In the wake of the surge, Walter detects Coral converging on the Central Ice Field, suggesting a massive deposit hidden there. Raven heads there to investigate, followed by Balam and Arquebus, but they are stymied by the PCA, who send their military forces and recovered Coral superweapons known as "C-Weapons" to suppress the corporations. Faced with the threat of the PCA, Balam and Arquebus form an impromptu alliance, and direct Raven to weaken the PCA by attacking them directly. The PCA's trump card, the Ice Worm, goes out of control and is destroyed by the corporate alliance. Soon after, Ayre reveals to Raven that she is actually an extraterrestrial rather than a human colonist, one of many formless, wave-based beings created by mutations in the Coral flow.
After crippling losses, the PCA are forced to withdraw from Rubicon. Without a common enemy, Balam and Arquebus resume hostilities and the three-way war between them and the RLF continues, though Arquebus quickly gains the upper hand by reverse-engineering PCA technology. Meanwhile, Walter sends Raven to explore an underground facility, Watchpoint Alpha, and discovers the ruins of Institute City, the site of the Coral deposit and the Vascular Plant, a megastructure created to extract Coral and send it into space. G1 Michigan is killed by Arquebus forces while trying to capture the Watchpoint, causing Balam to withdraw from Rubicon. Their dominance solidified, Arquebus forces led by V.II Snail seize Institute City and capture Raven, with Walter's fate unknown. Carla helps Raven escape, explaining that she and Walter were part of a group called Overseer, dedicated to stopping a doomsday scenario where Coral expanded exponentially into space. Carla has Raven help her commandeer the Xylem, a massive colony ship, putting it on a collision course with the Vascular Plant to completely annihilate any surviving Coral.
Raven faces a moral choice that determines which of two alternate endings the player will obtain. If Raven chooses to side with Carla, Ayre breaks off relations with them. Raven breaks the Arquebus blockade around the Vascular Plant and is forced to kill Rusty, who is actually fighting for the RLF. Ayre then attempts to stop the Xylem by taking control of Rubicon's orbital defense satellites and an unmanned Institute mech. Raven is forced to confront Ayre directly, and destroys her. The Xylem successfully rams the Vascular Plant and ignites the Coral stored within, creating an apocalyptic firestorm later dubbed the "Fires of Raven". In the aftermath, Raven's survival is left uncertain, while the PCA and corporations abandon Rubicon, the planet having been completely scoured of all life. In a recording left by Walter, he congratulates Raven for fulfilling his last wishes.
If Raven chooses to side with Ayre, they attack Carla while her forces are distracted repelling Arquebus. Carla is killed, but this triggers a failsafe program to lock in the Xylem's course. Ayre then tasks Raven with sabotaging the Xylem to cause it to crash harmlessly in the ocean. She also sends a request for assistance to the RLF, who rise up en masse to overthrow Arquebus. Rusty joins forces with Raven, and they manage to disable the Xylem's generators and ramjet engines. Rusty destroys the Arquebus blockade, while Raven kills V.II Snail. Walter, now under Arquebus mind control, arrives in his own Institute AC, killing Rusty and attacking Raven. Raven defeats Walter and narrowly escapes the Xylem before it crashes. Ayre thanks Raven for protecting both the Coral and Rubicon, though exactly how humanity and Coral can coexist remains uncertain.
A third, secret ending is available only after both previous endings were unlocked. In it, the mercenary support AI ALLMIND recruits Raven into the Coral Release Project, which seeks to achieve symbiosis between Coral and humans and forcibly evolve humanity. To further it, ALLMIND directs Raven to sabotage the corporations. Raven also kills the RLF's founder, Thumb Dolmayan, who once plotted to enact Coral Release alongside the wave-mutation Seria, but now deeply fears its drastic, permanent effects on the human race and compares it to "casting the die". Preventing Raven's capture in Institute City, ALLMIND seizes control of the Institute's weapons to slaughter the corporate forces. Walter and Carla commandeer the Xylem in a last-ditch attempt, but are also eliminated with Raven's help. With Raven's role complete, it is revealed that the AC pilots that died were mentally uploaded into a gestalt intelligence as part of Coral Release. ALLMIND attempts to assimilate Raven and Ayre into itself by dispatching Iguazu, now merged with a powerful Institute AC. Iguazu usurps ALLMIND's control to kill Raven, but is defeated once and for all. ALLMIND surrenders control of Coral Release to Raven and Ayre, who initiate it themselves. Coral spreads throughout the universe, while a symbiotically linked Raven and Ayre wake up on a distant planet, activating their AC alongside numerous others.
