The Avengers battle Loki in Asgard as the other realms fall.
Introducing characters: Hoarfen, Midgard Serpent
Synopsis for "A Day Unlike Any Other"
The Avengers prepare for the final battle against Loki in their own way. Stark is seen in a great forge in Nidavellir crafting a new suit of armor with the help of the Dwarf king while Ant Man and Wasp ride with Sif and the Valkyries. A flying ship from Alfheim carries Hawkeye and Black Panther along with the light elf Faradei. As for Loki, he prepares for his final moment of triumph. All of the heroes, sans Iron Man and Captain America, assemble on the Bifrost.
First comes Hulk, still wielding the Executioner's axe, and the Warriors Three. Ant Man and Wasp are next, with Hawkeye and Panther arriving soon after. They have to contend with an army made up of all manner of mythological creatures as well as traitorous Asgardians who have accepted Loki's rule. They triumph but not without taking a few bad scrapes themselves. They each bring the others up to speed on the developments of the past few episodes and agree to storm Asgard together.
Captain America is still trapped in Niflheim and attempts to persuade its ruler Hel to let him go. Seeing that she will not be able to tempt him to stay and that Loki will dispose of her after she is no longer useful, Hel offers Cap a deal: she will send him straight to the battle but if he dies, she gets his soul forever. Meanwhile, the attack on Asgard begins and Loki vows to destroy the Avengers in front of Thor before he is executed. To that end, Loki summons Hoarfen the Ice Wolf. With its immense size and ice magic, it tosses the heroes around but fortunately, Hel was true to her word and sent Cap right to them. He immediately forms a plan and rallies the heroes to victory. Loki gets increasingly frustrated as he watches the battle and this time it is Thor's turn to gloat.
Just then, the heroes use Hoarfen as a battering ram to breach the inner sanctum and the final fight begins. Loki is able to hold his own against all of them with his own powers enhanced by the Odinforce, and he shatters Cap's mighty shield just to demonstrate how unstoppable he is. He gloats some more and prepares to finish them off but Iron Man arrives in a flash of lightning, sporting a new suit of armor composed of Uru, the same kind of metal used to make Thor's hammer. The "man of science" and the god of trickery square off in the skies above while the Avengers split up to free Thor and find the source of Loki's power. Thor reveals that they have to sever his connection to Yggdrasil, the World Tree, in order to defeat him. Then he takes up his hammer once again and joins the fight.
Hawkeye, Panther, and Ant Man find Yggdrasil but are hesitant at first to destroy it considering that it's supposed to connect all of reality together. Ultimately, they see no other alternative and Ant Man uproots the tree, causing the Odinforce to drain from Loki and back into Odin, who awakens immediately. Understandably, he is not happy. This time exile will not be good enough. The Avengers return to Earth in triumph and earn the respect of the gods themselves. Loki's punishment is revealed to be much the same as it is in Norse mythology: a serpent will drip venom into his eyes until the end of time. Just when things seem to be returning to normal, Cap is accosted by someone who looks exactly like him. The man shoots him, then transforms into a green-skinned alien, stating that "the infiltration has begun".
At the end of the episode, Captain America is attacked by Skrull that has assumed his identity and appearance. This might suggest that season 2 might follow a "Secret Invasion" storyline.