Hal and the green corps are recalled by the Guardians because there is trouble stirring in the universe. all 3000 of the surviving Corps make an appearance, we see the history of Hal and how he came to be the predecessor of abin sur. We also see the moment when Krona was first banished from Oa. We learn of Krona's new power and see a minor skirmish that results in the demise of a few Corps members