Green Lantern, Vol. 2

Alan Scott is on Earth-Two when he encounters a meteor that temporarily gives him the ability to manipulate wood. Excited by this discovery, he heads to Earth-One to tell Hal Jordan, but at that point, it no longer works. Asking his ring for an explaination, he learns that the "meteor" was the disembodied mind of Krona, a rogue Guardian, who was devoted to seeing the origin of the Universe, despite the risk of universal collapse. He saw back far enough to see a hand manipulating it before he was exiled as energy, but after riding back to Earth-One in Alan's power ring, he can take corporeal form once more. When he takes mental control of Alan Scott and the Guardians of Oa, there doesn't seem to be much hope of Hal saving the day.