WARNING: The following article contains spoilers for The Green Lantern #1 by Grant Morrison, Liam Sharp, Steve Oliff and Tom Orzechowski, in stores now.
Ever since DC relaunched its entire line of comic books with DC Rebirth in 2016, readers have known that the Watchmen's Doctor Manhattan was at the heart of the new mystery of the DC Universe. Following the events of Flashpoint, reality had been re-written, continuity streamlined and characters either changed or completely erased to make way for the New 52.
But with Rebirth, we learned that Manhattan was the one responsible for these changes. Why? No one knows for sure yet, but Geoff Johns and Gary Frank's Doomsday Clock is bound to give us the answers sooner or later.
While the general manipulations of Doctor Manhattan, as well as hints to his presence in the DC Universe, have been greatly toned down since the start of Doomsday Clock, Grant Morrison and Liam Sharp's The Green Lantern #1 bring the godlike being's machinations back to the forefront. In fact, his interference might be what fuels this entire new series.
In The Green Lantern #1, Hal Jordan returns to Oa,, the GL Corps' homeworld, where he is tasked with a new mission by the Guardians of the Universe. In the central precinct, one of the Guardians leads Hal to the famed Book of Oa, which contains all of the history of the Green Lanterns, as well as prophecies about the future. The Guardian notes that a review of the Book was recently conducted, whereupon it was discovered that alterations had been made in the charted history of the Corps without the Guardians' knowledge.
As he explains this, we see a dark cloud hovering over the book of Oa, and at its center lies a large, bright blue Hydrogen atom icon -- an icon readers will recognize as Doctor Manhattan's. It would appear then, that the changes inside the Book of Oa were made by the all-powerful Watchmen character. And while the Guardians do not know that he is the one responsible, they did manage to notice the inexplicable changes to their history -- and by extension their future.
As a result, the Guardians simply can't trust the Book of Oa any longer. Whether this was a purposeful act by Manhattan, or simply a byproduct of his general manipulations still remains to be seen, though it's a reasonable assumption that he would view the the Guardians a possible threat, and rendering one of their basic staples unreliable could be enough to disrupt them.
Either way, the Guardians know that something great and terrible is out there, and they can now only rely on their assets -- assets like Hal Jordan.