Well, perhaps Percy could be reborn into a different era in the 'Percy Jackson New Life' fanfiction. Like, he's born in ancient Rome during the height of the Roman Empire. He has to navigate this new world with his old memories intact, and deal with the differences between the Greek and Roman pantheons. He might also meet versions of his old friends in their Roman forms and form new alliances and rivalries.
One idea could be Percy discovers an ancient underwater temple in the Mississippi River near New Orleans that's related to a long - forgotten sea god. Another could be he teams up with local demigods in New Orleans to fight off a group of malevolent spirits that are causing chaos in the city. Maybe he also has to navigate the complex social hierarchies among the different magical beings in New Orleans while on a quest.
One plot idea could be Percy having to team up with Hera to rescue a group of demigods who have been captured by an ancient monster. Hera, despite her usual aloofness, realizes she needs Percy's unique skills.
Perhaps a fanfiction where the New Gods create a sort of competition for demigods. Percy enters this competition and discovers that there are rules he's not used to, and he has to use his wits and skills in new ways to win. And along the way, he makes some unexpected allies among the new gods.
One plot idea could be that Percy Jackson somehow ends up in the world of 'New Girl' and has to navigate the apartment - sharing and relationship drama while also hiding his demigod powers. For example, he might use his water - controlling abilities in a creative way to solve a plumbing problem in the loft, all while trying not to arouse suspicion.
One idea could be Percy waking up in a new world where the Greek gods are unknown, and he has to start from scratch to regain his powers and find his friends. He could face new monsters that are a mix of modern and mythological threats.
One idea could be Percy and his friends getting trapped in a virtual game world that's a twisted version of their own. They have to use their demigod skills to defeat the digital monsters and find a way out.
Maybe Percy is sent on a quest to Atlantis because there are rumors of a traitor among the Atlanteans who plans to side with the Titans. Percy has to navigate the complex political situation in Atlantis and figure out who the traitor is before it's too late. He also has to deal with the Atlantean magic which is different from what he's used to.
One idea could be that Percy discovers a hidden realm within the world of the Wanderer. This realm has its own set of rules and challenges that he has to navigate. Maybe he meets new demigods there who have been lost for centuries.
One idea could be Percy having to make a deal with a minor underworld god to save Annabeth from a new and strange curse that's slowly draining her life force. He has to complete a series of tasks in the underworld that test his loyalty and courage more than ever before.
Well, perhaps the shield was once owned by a powerful demigod from the past. In the fanfiction, Percy starts having strange dreams about this demigod and the shield's true origin. As he investigates, he realizes that the shield holds the key to defeating a new, emerging evil that threatens not just Camp Half - Blood, but the entire world of gods and mortals. So, he has to figure out how to unlock the shield's full potential.