Monsters (Stuck in Your Head) (джен)

At last, Loki sighed and closed his book. “Thor, I don’t want to go back to Sakaar.”
“We won’t be going back to the Sakaar we know. We’ll hop into a different time.”
“Every Sakaar is the same Sakaar. It doesn’t matter if we set the dial to now or a thousand years prior. That planet never changes.”
With every dismissal from his brother, Thor found himself running out of arguments. “But I thought you loved it there!”
At this, Thor received a hard glare from Loki—one that was completely unreadable. But, no matter. Most of his brother’s looks were hard to decipher, anyway.
 
Thor comes up with the brilliant idea to use Stark’s time machine as an easy way to return to Sakaar to retrieve a precious item for Brunnhilde’s birthday. Though not the least bit enthused at the notion, Loki goes along with him anyway, and Thor soon discovers that returning to the planet—even for the briefest of moments—was perhaps the worst idea he’s ever had.
Set in a universe where Loki survived through Infinity War and Endgame.
Written for Whumptober 2021, prompt no. 24: Revenge.