Along with the likes of Iron Man 2 and The Incredible Hulk, Thor: The Dark World is considered one of the Marvel Cinematic Universe's less successful efforts. It's a testament to the MCU's overall quality that the "worst" of them still constitute decent entertainment, but The Dark World illustrated how close the franchise came to succumbing to complacency. It worked but encompassed a very routine story, with a traditionally heroic Thor facing off against a generic threat that failed to fire the imagination. The film's lackluster reception prompted a change of direction in the saga, and today, it stands out as an average movie in a franchise full of great ones.
As a result of that change, an intriguing Easter egg was left behind from the film's post-credits sequence. As Thor and Jane meet for a long-overdue embrace, a Frost Beast, brought from Jotunheim during the film's climactic battle, is seen frolicking in a London parking lot chasing pigeons. It's a clever joke, but many don't realize that creature may be a lot more powerful than the MCU has let on, which makes the mystery of what happened to it all the more pressing.
The Frost Beast Was a Formidable Foe for Thor and His Allies
The Frost Beast first appeared in the original Thor as the God of Thunder and his allies assaulted Jotunheim. They appear as gigantic predators with giant spiked tails and claws that let them grip the sides of glacial ice. Thor was able to kill the monster with his hammer, punching it through the back of its throat, but it still proved a formidable foe.
A second Frost Beast appears in The Dark World as Thor and Malekith battle between the Nine Realms, and the Convergence takes place. It reappears in London just in time to devour a Dark Elf menacing Darcy, altering its status as a mindless beast. The Frost Beast's next moment in the post-credits scene then keeps with the film's sense of humor and provides a cute coda to an otherwise run-of-the-mill Thor/Jane embrace. But since Thor and Jane's story ended there, only being picked up again in Thor: Love and Thunder, news of the monster's rampage across Earth was left dormant, leaving the door open for several possibilities.
The Frost Beast Could Become a Lovecraftian Nightmare in the MCU
While the MCU is perfectly capable of hand-waving the monster away, its appearance suggests it might be far more powerful than it seems. Some eagle-eyed fans have noted the creature's resemblance to Atum the God Eater, a Lovecraftian creature from the comics capable of devouring gods and consuming their energy. If that's the case, the creature's presence on Earth looks a lot direr, and while the lack of follow-up suggests that nothing untoward came of it, something that powerful is apt to draw attention.
It remains possible that the creative team at Marvel Studios is playing the long game, waiting for the perfect opportunity to reintroduce the beast, likely in something like Loki or a follow-up to Thor: Love and Thunder. However, that's still highly speculative, and there's a good chance that the Frost Beasts have no connection to Atum, in which case the romping creature at the end of The Dark World was likely attended to in a by-the-numbers manner. Thor or another hero could've returned it to Jotunheim, killed it or even put it on display at the London Zoo, none of which would merit any onscreen time in a franchise bursting with plot points. But the MCU always keeps its Easter eggs in reserve, and with Loki making both time travel and alternate realities a possibility, the Frost Beast may eventually prove to be a much bigger deal than he initially seemed.