Wonder Woman didn't realize it at the time, but something she said way back in the first issue of Dark Nights: Death Metal would end up prophesying the reason why the DC heroes' adventure later played out the way it did. This includes her ascent into the beyond with the Hands after having saved the Multiverse and created the Omniverse.
Originally, all Diana meant to convey that she had chosen a strategy she preferred over Batman's to overcome the impending existential threat facing their Multiverse (in addition to serving as a badass line before she dealt a fatal blow to The Batman Who Laughs). However, her simple, yet prophetic words would soon embody so much more than what she could have ever possibly foreseen: "But this isn't [Batman's] story."
Daring to Dream
At the start of the Death Metal series written by Scott Snyder with art by Greg Capullo, the Multiverse's first and most feared creator Perpetua is already nearing the end of her conquest against all creation. Meanwhile, The Batman Who Laughs holds dominion over the chaos left in her destructive wake by building worlds in his image. Batman believes that the only way forward is for Earth's last surviving heroes to just pursue small victories by attempting to only salvage what little Perpetua hasn't yet obliterated. But Wonder Woman can only think on a grander scale: To save everything that is already lost by creating their own crisis through Crisis Energy. So when she later tells The Batman Who Laughs that this isn't Bruce's story, Diana means that she's already fully committed to her much larger plan. She then proceeds to set everything in motion by ripping the monster apart, an act that spawns a much more dangerous foe: The Darkest Knight. While his creation spells certain doom for the Multiverse, it's also responsible for the Multiverse's salvation and rebirth.
Before the many twists that follow, Wonder Woman not only comes up with the initial plan to save their entire Multiverse, but would have single-handedly achieved this endeavor on her own if the Darkest Knight weren't so diabolically cunning. First, the so-called Ring Slingers attempt to dismantle antennae transmitting Crisis Energy to Perpetua, which fuels her rampant destruction. Meanwhile, Wonder Woman, Batman and Superman venture into the Dark Multiverse to find and redirect the source of that energy from three transpiring Crises to Wally West. While Wally West would save the day in this scenario, the entire plan is predicated on the success of Superman, Wonder Woman and Batman. The fact that both Superman and Batman later perish in this mission means that everything falls on Wonder Woman. She seemingly succeeds, and even recruits Superboy-Prime in the process, a prize that is especially remarkable considering he originally sold her and the rest of the Multiverse out so his world would survive during the Darkest Knight's rule. Unfortunately, the Darkest Knight, much like the Dark Knight himself, prepared by identifying all possible scenarios and foils their plan.
Becoming Truth Incarnate
After their first attempt fails, a new possibility comes in the unlikeliest of forms: Lex Luthor, who provides a new strategy that is wholly contingent on Wonder Woman, as the entire endeavor revolves around the pursuit of truth. For, as Luthor astutely explains in Death Metal #5, Superman seeks to pull out the best in humanity, Batman attempts to curb humanity's worst qualities, and Wonder Woman pursues truth.
Truth is the foundation of his plan because, rather than Crisis Energy, its success is predicated on Anti-Crisis Energy, which is synonymous with truth. Here's why: Those who wield Crisis Energy during Crisis events can create their own universes, like how the Flashpoint Crisis led to the New 52. Those who exist in these new universes have no recollection of their past lives, so they are unaware of the truth. Meanwhile, Anti-Crisis Energy unites all universes within a Multiverse where every separate story essentially becomes one massive tale. More importantly, every person remembers all of their previous lives before every Anti-Crisis event, so they are aware of the truth.
As the bringer of truth, Wonder Woman is the quintessential hero to herald this energy, but she can't do so on her own. She still needs to create what Luthor describes as a machine that "forces us to see the truth." So Diana descends into the Forge of Worlds to construct such a machine in Death Metal #5. But in a twist that is apparently quite characteristic of Death Metal, the Forge actually bonds with her and the Lasso of Truth, transforming her into truth incarnate.
Making The Ultimate Sacrifice
On the surface, Wonder Woman is the hero of Death Metal for essentially becoming the embodiment of truth and engaging the Darkest Knight in a final battle that literally takes them through the ages. But what makes her truly heroic is her ability to follow through on her quest for truth despite knowing two major consequences of her actions.
First, the fact that Anti-Crisis Energy connects the events of every universe is problematic because each universe or story essentially becomes one page in a much larger novel. So what happens on one page must still be true on the next. In other words, a character who dies on page two will still be dead on page three. This directly affects Batman and Superman as they both perished in Death Metal #4 after failing to divert the Crisis Energy to Wally West. The only reason why they exist is because Wonder Woman captured her Crisis Energy. Successfully wielding Anti-Crisis Energy would mean that, since Batman and Superman died before, they would be dead going forward in every universe within this interconnected Multiverse.
Second, she later learns that Perpetua's almighty family, the Hands, are enraged by the corruption permeating Perpetua's Multiverse and plan to wipe Perpetua's creation out of existence. Diana discovers later that saving the Darkest Knight would ironically ensure the survival of their Multiverse, as he's the only being capable of defeating these creators. He promises her that he would create a world where all of her friends would exist peacefully if she lets him live, even though their existence would be a lie. The fact that Diana pursues the truth even when she knows her most beloved friends will die and that the Hands will wipe everything she knows from existence convinces the Hands to not only spare, but restore their Multiverse. Her success soon transforms her heroism into the much more revered state of martyrdom as she makes the ultimate sacrifice: to "ascend" with the Hands to ensure the continual survival of the Hands' creation.
Creating Endless Possibilities
This act, however, accomplishes more than just saving a doomed Multiverse. The moment every universe connects with each other creates a chain reaction that culminates in the proliferation of Multiverses out of the original Multiverse - or an Omniverse. At the very center of this new Omniverse lie not just one but two central worlds: The world comic fans know and the Elseworld. The creation of the Omniverse makes sense according to the many-worlds interpretation of quantum mechanics where all possible outcomes can be measured by a separate world or universe. The fact that every universe is now connected and every person now has knowledge of every universe can lead to a plethora of more outcomes, universes, and Multiverses.
Additionally, the Hands are so impressed and even influenced by Diana's heroic actions that they literally personify their admiration and respect by actually taking her form when meeting her for the first time. Despite "ascending" with the Hands, Diana not only singlehandedly saves the Multiverse in Death Metal but creates an Omniverse where anything and everything is possible. Her decision to dream and reach beyond Batman's initial plan, her decision to pursue her purpose and what she represents, and her commitment to truth regardless of the consequences create an endless source of possibilities for DC Comics.