Another antagonist could be a powerful frost giant. If Percy is involved in protecting Asgardian interests related to Thor, a frost giant could be a major foe. They are strong and have their own motives for opposing Thor and his champion. They might see Percy as an easy target at first but soon realize his strength.
Well, it could be about Percy Jackson being chosen by Thor to be his champion. Maybe Percy has to go on quests that are related to Thor's realm, like dealing with frost giants or retrieving some powerful Asgardian artifact. He might use his water - controlling abilities in new and interesting ways in the context of Norse mythology.
In most Percy Jackson canon, there is no relation to Thor. However, in fanfiction, anything can be possible. It could be that the author has created a unique crossover where Percy Jackson has some connection to being the heir of Thor, perhaps through some magical or divine intervention that the fanfic writer has dreamed up.
There could be Annabeth. She is Percy's close friend and often plays a crucial role in Percy's adventures. In a situation where Thor kneels to Percy, she might be there to witness it and offer her own thoughts or reactions.
One possible reason could be that Percy has shown some extraordinary power that even Thor, a powerful god, respects. Maybe Percy has defeated a common enemy in a really remarkable way that makes Thor recognize his strength and kneel in admiration.
Well, in fanfiction, if Percy is the Champion of Pontus, his story would be filled with more mystery. Pontus is an ancient and powerful entity. Percy might be called upon to do things that go against the traditional ways of the Olympian - influenced world he's used to. He could discover secrets about the origin of the sea and his own powers that were previously unknown. This would not only make for an exciting read but also show how Percy can adapt and make his own path even when given a very different role.
One possible fanfiction could be about Percy Jackson seeking the guidance of Hestia, the goddess of the hearth, who has now become a champion in some way. Maybe she is a champion against a new threat to the demigod world. Percy could learn new skills or gain unique powers from her. For example, powers related to home and family, which could be used to protect Camp Half - Blood in a different way than before.
In fanfiction, Percy Jackson as the champion of Hades could bring a whole new dynamic. He might have to deal with the darker aspects of the Underworld. For example, he could be in charge of ensuring the souls are properly sorted, which is a huge responsibility.
In some fanfiction, Percy Jackson might be depicted as a champion of Kronos, but this goes against his character in the original series. In Rick Riordan's official books, Percy is a hero who stands against Kronos and his evil plans.
In Percy Jackson fanfiction, the 'Champion of the Sun' could be a character with special powers related to the sun. It might be someone who has the ability to control sunlight, perhaps for combat or to perform other extraordinary feats. Maybe they are a hero figure within the fan - created story, with a backstory that ties them to the sun in some way, like being blessed by a sun - related deity.