WARNING: The following contains spoilers for Wonder Woman #771, by Michael W. Conrad, Becky Cloonan, Travis Moore, Tamra Bonvillain and Pat Brosseau, on sale now.
While Wonder Woman may be accustomed to working for and against the Greco-Roman pantheon of gods, the Amazon superhero's cosmic adventures at the start of the Infinite Frontier era have placed her squarely amidst the Norse pantheon instead. Trapped in a seemingly endless cycle of life and death in Valhalla, Diana Prince is completely out of her element and cut off from her usual support network.
In order to break the cycle and return to the main DC Universe, Wonder Woman must dive headfirst into the dragon's maw, literally, as she allows herself to be devoured by one of Valhalla's most imposing monsters: The Nidhogg.
In Norse mythology, the Nidhogg is a massive serpent that gnaws at the roots of Yggdrasil, the World Tree that connects the various realms. Learning that the World Tree appears diseased and dying, Diana ventured to the roots that are trapping the Nidhogg to see if curing the tree's ailments will result in its restoration and Wonder Woman's eventual escape. As with Norse legend, the serpent is linked in permanent rivalry with an eagle roosting at the top of the World Tree, with Diana's squirrely new companion Ratatoskr granting Wonder Woman an audience with the eagle.
Realizing that the shell of one of the eagle's eggs is the only thing that will shield her from the Nidhogg's salivary acids, Wonder Woman and Ratatoskr persuade the eagle to spare one of her eggs as part of her longstanding feud with the Nidhogg so she can retrieve a key from the serpent's stomach. Breaking the egg in half, Wonder Woman positions herself close to the serpent, with the half-shell facing up, as Rataoskr offers the unsuspecting monster the eagle egg as a tribute. More voracious than cautious, the Nidhogg eagerly swallows the egg whole, Diana and all, none the wiser as to what actually transpired as Wonder Woman makes her most daring deception yet.
The Nidhogg, surprisingly, hasn't appeared predominantly in the Marvel Universe iteration of Norse mythology, with other serpents and dragons plaguing Asgard instead. A wood craving of the monster is briefly seen in 2011's Captain America: The First Avenger, with the Red Skull pressing the serpent's eye to discover the hidden Tesseract in a coastal Norwegian village. While Thor may not be on hand to help Wonder Woman in her own Norse odyssey, Diana is capable of outsmarting the Nidhogg to escape from the Northern European pantheon that she has called home for the past several life cycles.
Wonder Woman had the most important mission of all coming into the Infinite Frontier era, cruising the reborn DC Multiverse to discover what the true ramifications of the recent crossover event Dark Nights: Death Metal truly are. After completing her cosmic tour, Diana has been unable to share her findings with the other heroes, instead trapped in Valhalla with no discernible means to escape.
With her final fate linked to the survival of the World Tree, Wonder Woman has to save Yggdrasil at all costs and that includes taking the ultimate plunge inside of the realm's most ravenous monster. With a key somewhere in the Nidhogg's gullet, Wonder Woman has taken a page from Jonah to be swallowed whole by the leviathan. Thankfully for the Amazon, the Nidhogg isn't one to chew before swallowing.