A young and idealistic diplomat from Earth could be a main character. They initially try to avoid war but are pushed aside by the warmongers. As the war rages, they try to find a way to end it. From Asgard, Heimdall could be a main character. With his all - seeing abilities, he is constantly watching the Earth's moves and reporting back to Asgard, playing a crucial role in their defense strategy.
On the Earth side, it could be a military general who is leading the charge against Asgard. He might be a tough and battle - hardened character. On the Asgard side, Thor could be a main character, as he is one of the most well - known Asgardians. He would be trying to protect his home and people from the Earth's attacks.
Maybe a scientist on Earth who discovers something about Asgard that sets off the war could be a main character. They might be a bit of an anti - hero, thinking they are doing the right thing for Earth but actually causing chaos. For Asgard, Loki could also be a main character. He might be playing his own games during the war, either helping or hindering Asgard depending on his own motives.
In this fanfic, perhaps there's a power struggle. Some power - hungry group on Earth wants to take over Asgard's resources or technology. They manipulate the situation to make it seem like Asgard is a danger, so Earth goes to war. Asgard, on the other hand, is just trying to protect itself and its way of life.
He could also meet Odin. Odin might view Captain America as an interesting mortal from Midgard and might have some words of wisdom or a task for him to complete during his stay in Asgard.
He might be amazed by the grandeur of Asgard. Its golden palaces and powerful magic could both intrigue and intimidate him. Maybe he'd meet Thor and they'd exchange stories about their different kinds of magic and heroic deeds.
Well, perhaps Captain America could be on a mission to seek an ancient Asgardian weapon to help in the fight against a new threat on Earth. He might meet Thor and the other Asgardians, and have to prove himself worthy in their eyes, just like he did in his own world.
Since it's 'the lion goes to war story', the main character is most likely the lion itself.
Well, in this fanfiction, Tony might find himself in the middle of Asgardian politics. He could use his wits to help solve some internal disputes. Or perhaps he'll be challenged to a duel by an over - confident Asgardian warrior, and he'll have to use his Iron Man suit in a very different kind of battle environment than he's used to on Earth.
Well, he might get into fights with the Asgardian warriors. Maybe he'd show them some of his ninja skills and they'd be really impressed.
Miku could be a central character. She's one of the most well - known Vocaloids, and she could be leading the fight against an evil force trying to take over the Vocaloid realm.
I'm not sure without reading it, but there might be some brave Earth military commanders and perhaps some Romulan leaders.
I don't know as I haven't read the novel. But they could be diplomats, military leaders, or spies from the countries involved in the Cold War.