The sun of the Green Lantern homeworld, Oa, is becoming a gateway for Krona, an evil anti-matter alien tyrant that once sought to destroy all life. As precaution the Guardians of the Universe decide to evacuate Oa of all valuables, such as the Central Battery. While in line to charge their rings before the Battery is taken away, Green Lantern Corps rookie Arisia Rrab converses with Hal Jordan and expresses her self doubts as the newest Green Lantern. In response, Hal tells her the story of the first Green Lantern:
The First Lantern Avra, a scribe to the Guardians, is chosen by the final of the first four power rings despite having no skill or aptitude as a warrior. Avra and the other three original Green Lanterns, G’Hu, Wachet, and Blu, are immediately tasked with stopping the Dominators, an aggressive species which is invading solar system after solar system. Blu is the first Green Lantern killed in battle, whereupon with defeat apparently at hand Avra uses his willpower and imagination as a writer to continue the fight: He creates the first construct from his ring, a sword, which is used to wreak havoc amongst the alien war armada. Following Avra’s lead the other two Lanterns, G’Hu and Wachet, also create their own distinct power ring constructs, and the battle is won. The power to shape constructs from the power rings becomes standard operating procedure, and Avra rises in prestige among the growing Green Lantern Corps. After his death, Avra’s ring is passed down and ultimately comes into the possession of Abin Sur, who is then succeeded by Hal Jordan.
Back in line at the Central Battery, Hal and Arisia meet Kilowog, the head drill sergeant of the Green Lantern Corps. He antagonizes Arisia as a rookie, reminding her that she still has to attend boot camp. Hal tells Arisia not to fear Kilowog, and recounts the story of Kilowog’s own trainer.
Kilowog Sgt. Deegan trains the rookie Kilowog and others by removing their power rings and putting them in deadly settings such as a volcano about to erupt. Kilowog confronts Deegan and accuses him of employing a reckless training method and of having no value for the lives of his trainees. They briefly fight until Sgt. Deegan is called to deploy with his recruits when a nearby planet comes under attack by the Khunds, as they are the nearest Green Lanterns in the sector. Deegan purposefully drops Kilowog’s ring before departing with the other recruits, and Kilowog picks it up. In the battle Sgt. Deegan orders the rookies to protect the refugees as he deals with the invaders. As Kilowog catches up, Sgt. Deegan is mortally wounded. Kilowog destroys the army and goes to Deegan’s side. Deegan tells Kilowog he never would have let his rookies die and that he did what was best for their training. He passes his authority to Kilowog, who completes the mission.
Hal and Arisia arrive at a border patrol of the sun and await Krona’s return. Arisia and other Lanterns hear a Delphic prophecy from a Lantern named Laira who is levitating in the Lotus position (about which she remarks “That was strange.”), whereupon Hal shares Laira’s own story:
Laira Once a princess, Laira is sent on her first solo mission to her homeworld to deal with charges that her people are attacking the Khunds unprovoked. Standing in her way, Laira quickly defeats her father’s mistress and her belittling brother. But when she faces her father she is saddened to learn that the recent war crimes were his own decision. He has been driven into rage by the loss of honor that Laira’s ring chose her and not him when the Khunds attacked Jayd. Laira is ultimately able to defeat her father who admits she has truly earned her adulthood. He then commits ritual suicide to maintain his honor.
Back at the border patrol of Oa’s sun, every Lantern extant has been called to await Krona’s return, with the notable exception of Mogo. Hal explains who Mogo is and why he is not present:
Mogo Doesn’t Socialize Bolphunga the Unrelenting seeks to fight and destroy all the most powerful warriors in the universe. He is told, however, by his latest opponent (a volcanic being whom he dismembers) that he will never defeat the Green Lantern Mogo. Bolphunga’s computer contains no data on Mogo save for his whereabouts on a mysterious green planet. Bolphunga spends weeks there tracking Mogo’s plethora of power signatures, but never finds the elusive Lantern. He then sets explosives all over the planet in order to flush Mogo out, but is horrified when the planet extinguishes all the bombs and Mogo is revealed to be the entire planet itself. He attempts to escape, but Mogo easily captures him.
At Oa’s sun Hal and Arisia are attacked by Krona’s Shadow Demons and rescued by Sinestro. Sinestro then speaks of the prophecy that Oa will be destroyed and relates a story of Abin Sur and the Lantern view on destiny:
Abin Sur Hal Jordan’s predecessor Abin Sur fights Atrocitus, an alien criminal speaking dark prophecies. Abin Sur is assisted by Sinestro in capturing the alien. Sinestro and Abin Sur then have a conversation relating to the warnings that Atrocitus spoke and Sinestro insists that he does not believe in destiny. Parting ways, Abin Sur takes the criminal to the prison planet Ysmault where Atrocitus again speaks on Abin Sur’s imminent death. He also warns Abin that Sinestro will rise against the Green Lantern Corps and create his own lantern corps built on the power of fear. Abin Sur however refuses to believe his friend would betray his Green Lantern duties.
Krona finally arrives from the Oa Sun. All the Green Lanterns fight swarms of Shadow Demons as Krona, an enormous figure, rises from the sun. Many Green Lanterns are killed and all others fall back. It is Arisia who devises a plan: if Krona is made of anti-matter then an equal or greater amount of matter will destroy him on contact. The Green Lanterns fall behind the planet Oa and push it at Krona. Krona uses Shadow Demons to push back and the Corps finds itself stymied while taking casualties. However, Mogo the Living Planet arrives and uses its own mass and Lantern Power to assist his comrades. Oa and Krona are forced into the sun and both are annihilated. The prophecy of Oa’s destruction is fulfilled, but Krona is destroyed and the Corps is saved.
Mogo volunteers to be the Corps’ temporary base as they build a new Oa. Arisia is honored with an official entry into the Book of Oa for her heroic ingenuity, although she still has to report for Kilowog’s training.