In some fanfictions, a cool plot twist could be that Percy's connection to Kronos gives him the ability to travel through time. He could use this power to go back and change certain events that led to Kronos' rise or fall. But this also comes with risks, like accidentally changing things for the worse or getting trapped in a different time period.
One interesting 'Son of Kronos Percy Jackson' fanfiction could be one where Percy has to face his new identity as the son of Kronos while still trying to protect his friends at Camp Half - Blood. It might explore his internal struggle between the dark heritage of Kronos and his loyalty to his friends.
One possible plot twist could be Percy struggling with his heritage. Since Kronos is a rather evil figure in Greek mythology, Percy might have an inner battle against the dark tendencies that could be associated with his bloodline. He could constantly fight the urge to be cruel or power - hungry like his father was known to be.
One possible plot twist could be that Percy meets his own parents at a different time than expected. For example, instead of seeing his mother as he knew her, he might encounter her as a young girl. Another twist could be that Kronos has some ulterior motive for sending Percy back that Percy doesn't initially realize, like changing the course of events to actually benefit Kronos in the long run. Maybe Percy discovers that by changing certain events in the past, he's unknowingly setting up a different future that Kronos can manipulate more easily.
A really cool plot twist could be Percy finding out he has a long - lost sibling who is on the side of the Titans. This would create a huge internal conflict for Percy as he has to decide between his loyalty to his new - found family and his duty to the Olympians. It would also add a lot of drama and tension to the story as he tries to sway his sibling to the right side.
Another plot could involve Percy being sent on a quest by the gods to find a way to sever his connection to Kronos completely. Along the way, he meets new allies and enemies, and has to face challenges that test his loyalty to both his new identity and his old friends.
Perhaps a plot twist could involve Kronos' essence trying to take over Percy's body. Percy would have to fight against this internal takeover, and in the process, he discovers a way to use Kronos' power for good. This would completely change the dynamics of the Percy Jackson universe as we know it, with Percy becoming a sort of anti - hero figure who uses the power of the enemy to protect his friends and the world.
In some fanfictions, a really cool plot twist could be that Percy's Hela - given powers are slowly corrupting him. He starts to see the world in a different, darker way. His friends notice the change in him but don't know the cause at first. As he struggles with this corruption, he has to find a way to either embrace it and use it for good in a new way, or find a way to get rid of it. Also, imagine if Percy discovers that he has a half - brother or sister from Hela's side in the Norse world, and this new relative has a completely different view on life and power, which causes more drama and conflict for Percy.
One idea could be Percy struggling with the dark influence of Kronos while still trying to maintain his loyalty to his friends at Camp Half - Blood. Another could be Percy having to hide his true identity as Kronos' adopted son from his closest allies. Maybe he discovers some long - lost powers or knowledge that Kronos had hidden away for him, which he must use to either save or destroy the world of the gods.
One idea could be Percy having to choose between the powers of Kronos and Gaea. Another could be Percy teaming up with some unexpected allies from the realms of Kronos and Gaea to fight a new common enemy. Maybe Percy discovers a hidden prophecy that involves his lineage as the son of Kronos and Gaea and has to fulfill it to save the world.
A great plot could also involve the OC forming an unlikely alliance. He could team up with some of Percy Jackson's friends, like Annabeth. They initially don't trust him, but as they face challenges together, they realize that he's not like his father. This alliance could lead to them facing off against an ancient evil that only the combined knowledge and powers of the OC and the other demigods can defeat.