Perhaps some of the demigods from other camps that he didn't interact much with before could become his new allies. They might see his leadership during the war and want to be part of his group, to learn from him and fight alongside him in any future conflicts.
There could be new demigods. Maybe some who were hidden during the giant war and now come out. For example, a demigod of a less - known god or goddess.
Some of the Greek heroes like Achilles could be Percy's allies. Percy might learn a lot from Achilles about combat and heroism. And there could be some new characters created specifically for this fanfiction, like a young seer who can predict the outcome of battles and helps Percy make the right decisions.
It could be a rogue demigod who was on the losing side of the Giant War and is now seeking revenge. This demigod might have found some dark power or be allied with some minor but dangerous mythical creatures.
In fanfiction, Percy might finally get some peace. He could go back to school and try to have a normal life, but still be on guard for any new threats. Maybe he'd focus more on his relationship with Annabeth and they'd plan for their future together.
One possible plot could be Percy and his friends dealing with the aftermath of the war in the mortal world. Maybe they have to hide their demigod identities even more carefully as the war has drawn some unwanted attention. They could also be working on rebuilding Camp Half - Blood and trying to make it safer for new demigods.
In the fanfiction, Percy might face new challenges related to his demigod status. Maybe he has to deal with the aftermath of the war, like rebuilding Camp Half - Blood or helping new demigods adjust.
Maybe there is a scientist or an inventor who becomes Percy's ally. This person could be creating new weapons or gadgets that Percy uses in battle. Their alliance could be crucial in giving Percy an edge in the fight. For example, the inventor might create a special type of grenade or a device that can jam the enemy's communication lines.
His old friends from Camp Half - Blood like Annabeth could be his allies. She would support him through the transition of becoming a god. Grover too, as his long - time friend, would be there for him. Also, some of the minor gods who have always been on good terms with Percy, like Hestia, might offer their help and guidance as he steps into his new role as a god.
Perhaps some minor gods who have been overlooked in the past. They could see Percy's new status as the 'Son of the Universe' as an opportunity to gain more influence and decide to ally with him. For example, the god of small rivers or the goddess of wildflowers.
Another option could be a new demigod. A character who was not very involved in the war but is now thrust into the post - war chaos. This new character could bring a fresh perspective and could be learning about the demigod world and its history while also trying to help in the rebuilding and healing process.