Well, it could involve Percy being tasked with protecting Artemis in a way that goes against his normal alliances. Maybe some dark force is after Artemis and Percy has to use his skills in a new and unexpected way.
The plot might revolve around Percy being framed as an assassin of Artemis. He then has to clear his name while also dealing with the chaos that such an accusation brings to the demigod world. He might have to team up with some unlikely allies to prove his innocence and find the real culprit.
Perhaps in this fanfiction, Percy is under a spell or some kind of mind control that makes him seem like an assassin of Artemis. The story could be about how his friends try to break the spell and save him from himself, all while Artemis is conflicted about whether to trust Percy or not. There could be a lot of action as they battle the source of the mind control and try to restore order.
Obviously, Percy Jackson and Artemis. Percy is the main character of the original series, and since he's the 'assassin' in this fanfiction, he's central. Artemis is the one he's wrongly accused of trying to assassinate, so she's also a key character.
In this fanfiction, it could be that Artemis is in a situation where she is about to be killed or lose her powers forever. Percy, being the selfless hero he is, takes on a deadly task to prevent that from happening. Maybe it involves facing an ancient and malevolent god who has a vendetta against Artemis, and Percy uses his unique abilities and the element of surprise to try and stop this god, but at the cost of his own life.
One possible plot could be that the son of Artemis discovers a threat to the demigod world that is related to his mother's domain. He then seeks out Percy for help because of Percy's reputation. Together, they embark on a journey to find a magical artifact that can stop the threat.
One possible plot could be that Percy, being raised by Artemis, grows up with a deep connection to nature and the moon. He might be trained in archery and hunting from a young age. Since Artemis is a virgin goddess, Percy would have to deal with the unique situation of being part of her all - female group, perhaps facing some initial resistance from the hunters. He could also develop special powers related to the moon or gain an enhanced sense of stealth.
In a 'Percy Jackson adopted by Artemis' fanfiction, perhaps Percy is exiled from Camp Half - Blood due to false accusations. Artemis, who has always been intrigued by Percy's courage, takes him in. With Artemis as his new guardian, Percy gets involved in the Hunters' battles against ancient monsters that threaten the world. He also has to deal with the jealousy of some of the other Hunters who are not happy about a male being in their midst.
One possible plot could be Percy having to defend Artemis from a new and powerful enemy. Maybe a primordial being has awakened and is targeting Artemis. Percy, with his skills and the help of his friends, must fight this enemy. He could also have to deal with the politics among the gods as he tries to protect Artemis, since some gods might not be so happy about his interference.
Well, in many fanfictions, Percy might be on a mission to assassinate some powerful being in Tartarus. Maybe he has to face all kinds of hellish creatures and overcome insane challenges. It could involve him using his water powers in unique ways, like creating weapons out of water to fight the demons of Tartarus.
Well, it could be about the son having unique powers. Since Percy has control over water and Artemis is a powerful goddess, the son might have some sort of combination like the ability to control water in a lunar - influenced way. Maybe he can create ice sculptures during a full moon or something.
A possible plot could be that Percy is initially unaware of his true parentage. He grows up with normal demigod problems, but strange things start to happen. He has an unusual affinity for the moon and animals, which are associated with Artemis. As he discovers the truth, he is caught in the middle of a power struggle between the gods. Some gods want to use him for their own purposes, while others want to destroy him. Percy has to fight to survive, make allies, and figure out his place in this new and dangerous world. He also has to deal with his feelings towards Artemis, who is not like a typical mother figure.
Well, it could be about Percy having to deal with the conflict of being the son of two such different deities. Maybe he has powers from both Orion and Artemis. For example, he could have Orion's hunting skills combined with Artemis's connection to the moon. He might struggle to fit in with the normal demigods as his origin is so unique.