Green Lantern Vol 2 #40
Cover Artists: Gil Kane, Murphy Anderson
"Secret Origin of the Guardians!"
Writer: John Broome
Penciler: Gil Kane
Inkers: Sid Greene
Appearing in "Secret Origin of the Guardians!"
Featured Characters: Green Lantern (Hal Jordan)
Green Lantern (Alan Scott)
Supporting Characters: Guardians of the Universe
Villains: Krona Next (First appearance)
Other Characters: Ki-Nilg (First appearance) (Flashback only)
Synopsis for "Secret Origin of the Guardians!"
On Earth-Two, Alan Scott is shocked to find that his power ring is not working against a yellow meteor, and yet it is able to save Doiby Dickles' car from a falling tree. Realizing that his power ring seems to have the same properties of the Earth-One Green Lantern, Hal Jordan, Scott travels to Earth-One to tell his alternate reality counterpart of his discovery. However, when Alan tries to show Hal what his power ring can do on Earth-One, he finds that the effect has worn off. Realizing that there might be more going on, Hal suggests they probe Alan's power ring to find out what happened.
The ring begins by explaining that millions of years ago on the planet Oa on Earth-One, a scientist named Krona tried to view the creation of the universe with a device -- something that was forbidden by the Oa society -- however in viewing creation he caused a chain reaction that destroyed his device and created evil in the universe. As punishment, Krona was converted into energy and sent to spend eternity circling the various universes in existence. The Oans then created the Green Lanterns to police the universe and defend it from evil. The ring then explains that the yellow meteor that Alan tried to stop was really Krona, who was able to then transfer his being into Alan's power ring to piggy back into Earth-One.
Not wishing to be interrupted by the two heroes, Krona uses his mental powers to manipulate the Guardians to come to Earth, and demands that Hal turn his title of Green Lantern over to Alan Scott. While Hal is shocked by this revelation, Krona takes control of Alan's body and attacks Hal with it. With Hal defeated, Krona has the Guardians brought to his hideout while the spirit of Alan Scott helps Hal track down it's location. Hal battles Krona and destroys his machine and frees the Guardians. The Guardians then banish Krona once more, and once Alan is restored to his body, the two Green Lanterns part company, Alan returning back to Earth-Two.
This issue told the origin of the Guardians of the Universe and established that the DC Universe was comprised of an infinite number of parallel earths, populated by different versions of Earth-One's heroes.
This issue is reprinted in The Green Lantern Archives Vol. 6.