I think Nico di Angelo could also be a central character. He has his own unique powers and backstory, and after the giant war, he might be involved in some of the darker or more mysterious aspects of the post - war world, like dealing with any remnants of the Underworld's connection to the giants' plans.
Annabeth Chase would also be a main character. Her intelligence and strategic skills would be important in the rebuilding efforts. And of course, her relationship with Percy is a major aspect of the story.
Well, the characters might face new threats that emerged after the giant war. For example, some leftover magical creatures that were once under the giants' control could now be causing chaos. Also, they could have to deal with political unrest within the Olympian world as different gods vie for power in the post - war situation. There could be new quests to retrieve powerful artifacts that were lost during the chaos of the giant war. And of course, there could be new relationships forming among the heroes, both romantic and platonic, which would add more depth to the story.
Definitely Percy Jackson. He's one of the central characters in the 'Heroes of Olympus' series, so it's very likely he would be involved in a time - traveling adventure.
Jason Grace is one of the main characters. He has leadership skills and is a son of Jupiter. He plays a crucial role in many of the group's adventures.
Naruto is a must - have main character. He's the one who would likely drive the story forward with his determination and unique abilities. Then there could be characters like Hercules from the Olympus side. He and Naruto could have an interesting dynamic, maybe starting as opponents and then becoming friends. And Sakura could also be a main character, representing the medical ninja skills in this strange crossover world.
Leo Valdez is another character who could be a star. His ability to create and manipulate fire can add a lot of excitement to party games. He could be involved in a game where he has to use his fire to light up targets or keep a magical fire - based object alive for a certain amount of time.
Tris and Four would likely still be main characters. Their relationship has been a central part of the Divergent series, and in a post - war scenario, they would be key in leading the rebuilding efforts or in bringing about change.
Some of the main characters are Percy Jackson, Annabeth Chase, Jason Grace, Piper McLean, etc.
The golden trio, no doubt. Harry, who has to find his place in a world that has changed so much after the war. Ron, who might be exploring new career opportunities in the wizarding world. Hermione, who could be using her knowledge to bring about positive changes. And don't forget their families. The Weasleys, especially, would be an important part of their post - war lives as they are like a second family to Harry.
Percy Jackson himself is almost certain to be a main character. After all, the fanfiction is centered around him after the war. Annabeth Chase would also likely be a main character, as she is Percy's love interest and a powerful demigod in her own right. Grover, Percy's best friend, would probably be there too, still looking out for nature and helping Percy in his new adventures.