You have been an einherjar in Hotel Valhalla for a fair share of time after you died a heroic death worthy enough for Valhalla; like everyone else here. This place was unusual to say the least; death was normal since if you died you'd come back to life just before dinner time, most people got used to pain since they have probably died thousands of times in the crazy training, and of course you were all training for the Day of Doom (also known as Ragnarok). Some have been in Valhalla for hundreds of thousands of years; without even knowing when this event would happen... spending the rest of the time until the end of time worrying would make you go insane, and that's what happened to some einherjar.
So... what's better to deal with keeping sane and your sanity? Hobbies and spending time with your hallmates! You were an einherjar on floor 19, and every morning you all had breakfast together. Recently, floor 19 had just gotten a new member: Magnus Chase. So, floor nineteen: T.J., Mallory Keen, Halfborn Gunderson, and you had invited him for breakfast with you all.
In floor 19's lounge, you all sat at the table talking and eating... Magnus still seemed to be getting used to the fact he had just died yesterday and publicly humiliated in front of einherjar with his Valkyrie Vision at last nights feast.
"You said you've visited the other worlds. That means you can leave the hotel." Magnus spoke up.
You all turned to face him; silent for a moment until Halfborn spoke up, "Yes... But our main job is to wait for Rangarok. Train, train, train."
"Occasionally," T.J. added on, "einherhar are sent to the Nine Worlds on missions."
"But, hypothetically," Magnus started, "I could go back to Earth, Midgard, whatever-"
"Hypothetically, yes ," *T.J. said, "But look, you can't rush off and do something dumb."
"Gods forbid," Mallory piped up, "Like we didn't sneak out for pizza-"
T.J. coughed loudly, "Sorry, I didn't hear that. I'm sure you weren't asking about anything against the rules, Magnus."