WARNING: The following article contains major spoilers for Avengers: Infinity War, in theaters now.
If you haven't heard, the ending to Avengers: Infinity War doesn't leave Earth's Mightiest Heroes feeling like they gained a victory against Thanos. Not only did the Mad Titan assemble all six of the Infinity Stones, he also wiped out half of the galaxy's population with a snap of his fingers.
The Avengers and Guardians of the Galaxy that fought Thanos on Earth and his home planet of Titan were barely able to leave a mark on the villain. The only time Thanos was physically injured at all was in Wakanda, when Thor drove Stormbreaker, his new Asgardian weapon, into the Mad Titan's chest before the finger-snapping took place.
Thor's Infinity War arc led him to Nidavellir in search of Eitri (Peter Dinklage), King of the Dwarves, in order to have a Thanos-killing weapon forged. And seeing as how Stormbreaker nearly turned the tide in Infinity War, the Avengers would be wise to regroup, find Tony Stark on Titan, and make a trip to Nidavellir to arm themselves with some more Asgardian weapons if they hope to defeat Thanos.
The Avengers' trinity of Iron Man, Captain America and Thor have all lost their signature weapons: Thanos literally beat Iron Man's Bleeding Edge armor off his body, Cap relinquished his star-spangled shield in Captain America: Civil War, and Mjolnir was shattered in Thor: Ragnarok. After witnessing Stormbreaker's impressive debut, just imagine the excitement in theaters if Iron Man and Captain America were gifted magical artifacts as well. What makes this scenario even more plausible is there are examples of this happening in the Marvel Universe.
The 2011 event series Fear Itself saw Marvel's superheroes face off against the Asgardian God of Fear, who also happens to be Odin's brother and Thor's uncle. To combat the evil forces marching against them, called the Worthy, a collection of heroes were taken to Asgard and given magical mystical weapons, turning them into the Mighty. As you can see above, almost every member of the Mighty already appears in the Marvel Cinematic Universe, minus Wolverine. The only other person not likely to show up in Avengers 4 is Netflix's street-level hero, Iron Fist.
Captain America's shield was also a casualty of Fear Itself after being broken into pieces, which resulted in a new shield being built, mixing in the Asgardian metal Uru -- also found in Mjolnir. Of course, the MCU's Cap already has new Vibranium shields thanks to Black Panther, but there's no rule saying an upgrade can't be made for the next movie. Afterall, Iron Man's armor has changed multiple times throughout the MCU.
Let's also remember how Hulk refused to show himself after being soundly beaten by Thanos in the opening minutes of Infinity War. That left Bruce Banner to don the Hulkbuster armor in the battle of Wakanda. Instead of his cousin Jennifer Walters making her MCU debut in Avengers 4 as an Asgardian sword-swinging She-Hulk, Bruce could be the one wielding a sword. Adding Eitri to Avengers 4 also has the added benefit of another guest-appearance by Peter Dinklage, whose surprising cameo in Infinity War was one of the many highlights of the film.
The Avengers will have to get creative if they hope to undo the damage caused by Thanos' genocidal plans. If the untitled film really is the swan song for actors such as Robert Downey Jr., Chris Evans and Chris Hemsworth, then what better way to ride into the sunset than by Bifrost and an assist from one of the Nine Realms.