Perhaps Percy becomes king of a new realm created by the gods as a test. In this realm, he has to unite different mythical creatures who are at odds. He uses his leadership skills and powers to bring peace, and along the way, he uncovers secrets about the gods' true intentions in creating this place.
One idea could be Percy discovers a hidden underwater kingdom where he is hailed as a long - lost king. He has to deal with the politics and power struggles there while also protecting his friends from the new threats this kingdom brings.
One idea could be that the Phoenix King has a connection to an ancient prophecy in the Percy Jackson world. Maybe he is the key to saving Camp Half - Blood from a new, powerful enemy. For example, his powers of rebirth could be used to revive a fallen god who is crucial in the fight against the enemy.
Well, perhaps in the fanfiction, the Hellhound King has a connection to an ancient prophecy. Percy is tasked with either killing it or taming it to fulfill the prophecy. As Percy delves deeper, he realizes that the Hellhound King has a complex personality and motives that are not just about destruction. It could also be that the Hellhound King has a hidden lair full of secrets and treasures that Percy needs to explore for some reason, like to find a weapon to defeat a new threat.
Perhaps the Beast King is actually a misunderstood creature, and Percy has to convince the other demigods that they should work with him instead of against him. In this fanfiction, Percy could go on a journey to learn the true history of the Beast King and uncover secrets that change everyone's perspective.
One idea could be Percy having to face a new threat that is a combination of ancient Greek monsters that have merged into one super - monster. Another could be Percy trying to reform the Olympian council to make it more fair for demigods. Maybe he could also go on a quest to find a long - lost artifact that has the power to change the balance of power in the Olympian world.
One idea could be Percy having to face a new, powerful enemy that is a threat to his newfound position as king of the gods. This enemy could be a primordial being that has been awakened. Another plot could involve Percy trying to reform the rules among the gods, which causes a lot of internal conflict as the other gods resist change. And perhaps Percy discovers a long - lost prophecy related to his kingship that changes everything he thought he knew.
One idea could be Percy having to form an unlikely alliance with the Dragon King to defeat a common enemy, like a new and powerful Titan. The Dragon King might have his own motives and secrets that Percy has to figure out during their partnership.
One idea could be Percy facing a new and powerful enemy that is immune to water, which forces him to develop new skills. Another could be Percy becoming a king in a new underwater realm and having to deal with political intrigue among the sea creatures. Maybe he has to unite different mythological groups under his leadership to face a common threat like an ancient primordial being awakening.
One idea could be that the Primordial King emerges from a long slumber and Percy has to figure out a way to either ally with him or stop him from wreaking havoc on the demigod world. Maybe the Primordial King has some ancient knowledge that could help Percy in his fight against the Titans or other enemies, but at a great cost.
One idea could be Percy having to form an uneasy alliance with the Demon King to stop a greater threat that endangers both the demigod and demon worlds. Maybe a powerful ancient evil is rising and they have no choice but to work together, despite their initial distrust.
Another plot could involve Percy being tricked into taking on the role of king by a devious god who wants to use him as a puppet. Percy then has to figure out how to break free from this god's control and truly claim the throne for himself and for the good of all the demigods and mortals. He could seek the help of the wise centaur Chiron who gives him advice based on ancient knowledge.