Perhaps Thor visits the tree to find answers about Loki's true nature. The tree could be a sentient being that shares with Thor memories of Loki's childhood or his hidden desires. This could lead Thor on a path to either redeem Loki or face a new threat together with him.
The plot could involve Thor being led to Loki's tree by a vision. He arrives there and discovers that the tree has some sort of magic that is tied to Loki's past or future. Maybe it holds the key to saving Loki from a great danger.
There may be a fanfiction where Thor visits Loki's tree as a symbol of their connection. It could show Thor reflecting on their past, all the battles and reconciliations. The tree might be a place of power or a place where Loki left something important, and Thor is there to uncover its secrets.
Maybe Loki is betrayed by someone he thought was a friend, and he is deeply hurt both physically and mentally. Thor discovers what has happened. He becomes extremely protective. He first takes care of Loki's wounds, using his own knowledge of healing herbs. Then he sets out to find the one who betrayed Loki. Along the way, Thor makes sure Loki feels safe and loved, constantly reassuring him that he will always be there for him. This journey not only heals Loki's physical and mental wounds but also deepens their brotherly bond.
In this fanfiction, perhaps Thor hits Loki with Mjolnir as a form of punishment for one of Loki's many tricks. Maybe Loki has double - crossed Thor in a plan to take over Asgard, and Thor's only option to stop him is to use his powerful hammer.
Well, one possible plot could be that Thor and Loki's little sister has some special powers that are a mix of their own. She might be caught in the middle of their feuds, trying to bring peace between them. For example, she could use her powers to stop Loki from his mischievous plans that would anger Thor, while also making Thor understand Loki's motives better.
Well, perhaps Loki freezes Thor as part of a deal with an enemy. Thor is frozen and the enemy thinks they can now easily take over Asgard. But Loki has a hidden agenda. He freezes Thor not to harm him but to protect him from a more dangerous plot. Thor, while frozen, has visions or dreams that give him some new power or knowledge. When Loki finally unfreezes him, Thor is stronger and together they outwit the enemy and Loki's true loyalty is revealed to Thor, strengthening their bond.
One possible plot could be that Laufey, Loki's biological father, decides to use Loki against Thor. He might abuse Loki in some way, either physically or emotionally, to make Loki do his bidding, which could involve causing trouble for Thor. Loki, being in a difficult position, has to deal with his complex feelings for Thor while also trying to escape Laufey's control.
A plot development could be Loki forming an alliance with the Jotuns against a common enemy. This enemy could be a threat to both Jotunheim and Asgard. Loki, being in Jotunheim, has the opportunity to broker this alliance, which would surprise Thor and the other Asgardians when they find out.
It could be a very emotional reunion. Thor might be initially angry at Loki for all his past misdeeds but then quickly soften as he realizes how much he has missed his brother. Loki, on the other hand, might be a bit guarded at first, still not fully trusting Thor's reaction. But eventually, they would embrace and start to rebuild their relationship.
In the fanfiction, Thor could be a key factor in Loki's development within the TVA. Since Thor has always had a strong influence on Loki, his presence might make Loki question his actions and motives even more deeply. For example, Thor could remind Loki of their past, both the good and the bad times, which could lead Loki to make different choices within the TVA's framework.
There's 'Thor's Redemption in Loki's Arms'. In this story, Thor realizes his true feelings for Loki after a series of events that nearly tear Asgard apart. It's a tale full of emotion and character development.