 When Saint Walker was trapped in the Book of the Black by Lyssa Drak, Hal passed his ring on to Kyle Rayner so that Kyle could use it to fight off the Green Lanterns under Krona and Parallax's influence.Although Kyle was able to master the blue ring to use its power to at least temporarily cure some of the Green Lanterns pursuing them from Krona's influence, he was unable to cure Mogo before John Stewart was forced to destroy it, although Kyle was later able to use the blue ring to purge Guy Gardner of the side-effects of his use of a Red Lantern ring.With Guy cured, Kyle returned to his green ring, Walker reclaiming his blue ring after Krona's defeat.