The Hulk might not care much at first and just see her as another potential threat. But if she proves to be friendly, he might just grunt and accept her presence. Hawkeye would be suspicious, having been under Loki's control before. He'd be watching her every move closely. Thor would have the most complex reaction. He loves his brother deep down despite everything, so he might be more open to the idea of his daughter being different. He could try to mentor her in a way, to keep her on the right path. And the Avengers as a whole would probably have a lot of meetings and discussions about whether to trust her or not, based on her actions and words.
Thor might be conflicted. He'd see his nephew/niece but also remember Loki's treachery. Iron Man would probably be sarcastic at first, making remarks about the family genes. Captain America would be more cautious and diplomatic, wanting to give her a chance but also being on guard. Black Widow would try to read her body language and motives right away.
Some of the Avengers, like Thor, might have a more complex reaction. Since he is Loki's brother, he may feel a sense of responsibility towards the children. Others like Captain America would be cautious but fair, trying to assess if they are a threat. Iron Man, on the other hand, would probably be sarcastic and make some snarky remarks while sizing them up.
Tony Stark would probably be very intrigued. He'd want to study Loki's Jotun form, maybe even make some snarky comments about his blue skin. Steve Rogers, on the other hand, would be more cautious. He'd be ready for any potential threat that Loki might pose.
When the Avengers meet Lady Loki in fanfiction, their reactions would vary. Iron Man would probably start analyzing her, trying to figure out her weaknesses. Captain America, being the moral compass, would try to give her a chance to prove herself, but also be ready to fight if she betrays them. And Thor, he would have a mix of emotions, part anger from past experiences with Loki and part curiosity about this new form of his 'brother'. The more impulsive members like Hulk might just see her as a threat and react accordingly.
Well, Thor might be a bit shocked at first. He'd probably be amused by some of the wilder interpretations of his brother in the fanfiction. Captain America, on the other hand, would likely be confused by the whole concept as it's so different from the traditional stories he's used to. Iron Man would probably make sarcastic comments about how creative the fans are in coming up with these stories.
They might be cautious. After all, they don't know her and she's from Percy's world which could be full of unknowns for them.
Thor would likely be the most affected. He has a history with Fenrir as it is from Asgardian mythology. He might be cautious at first, but also feel a sense of kinship. Iron Man would probably be all about analyzing Fenrir, trying to figure out its weaknesses and strengths. Captain America would be on guard, ready to defend his team, but also open to the idea of Fenrir not being an enemy if proven so.
If Loki impersonated Thor, the real Thor would be furious when he found out. The other Avengers, like Iron Man, might initially be confused but then quickly realize something is off. Iron Man would likely use his technology to detect the impostor. Hulk might just smash first and ask questions later when he senses something wrong with 'Thor'.
Obviously, the Avengers would be the main characters. That includes Iron Man, Captain America, Thor, Hulk and others. And of course, Loki's son. He would be a central figure as well, with his own motives and backstory that would drive the plot.
Some would be intrigued. Captain America, being an open - minded person, might be interested in seeing different interpretations of their team dynamics. He could even gain new insights about his relationships with his fellow Avengers through the fanfiction.
She could fit in as a strategist. Since Loki was known for his cunning, she might inherit that trait and be able to come up with clever battle plans for the Avengers.