Another plot twist could be that Reyna loses her memories. This forces her to rediscover who she is and her place in the demigod world. In the process, she might form unexpected alliances or discover new powers she didn't know she had before. It also gives other characters a chance to interact with her in a different way as she's no longer the confident leader they knew.
A really interesting plot twist is when Reyna is chosen to be the vessel for a powerful ancient spirit. This spirit could be either good or bad, and it would greatly influence her actions and decisions. It could lead to a situation where the other characters have to decide whether to trust her or not, as she may be acting under the influence of the spirit rather than her own will.
A really interesting plot twist in fanfics about Percy and Luke is when the roles are reversed. Luke becomes the hero, and Percy is the one who is on the verge of turning to the dark side. It makes the readers see the characters from a whole new perspective. Another plot twist could be that they both get transported to a different dimension where they have to rely on each other completely to survive and get back home.
One interesting plot twist could be that Percy discovers a new power within the gamer - like world that he didn't know he had. Maybe he can suddenly control the elements in ways he couldn't before, like creating ice sculptures out of thin air when his main power was water - based before.
One idea could be that Percy and Reyna team up to go on a quest to find a lost magical artifact that has the power to restore a dying realm. They face various mythical creatures along the way and start to understand each other's strengths and weaknesses better.
In some fanfictions, a cool plot twist is that the daughter of Zeus has a power that is only activated when she is in great danger. So, in a battle against a powerful enemy, she suddenly reveals this new power that completely turns the tables. It could be something like the ability to create duplicates of herself, confusing the enemy. Another plot twist could be that she has a hidden bond with a certain weapon, like a sword that has its own consciousness. The sword might choose her as its wielder, and together they have powers that are far greater than expected. And there could be a plot twist where she discovers that Zeus has been keeping a big secret from her about her mother, and this secret changes her whole view of herself and her place in the world of demigods.
One possible plot twist could be that Artemis's blindfold is actually a self - imposed thing to gain a new power, and Percy discovers this secret halfway through the story. This would completely change their dynamic as Percy realizes he may not have been needed as much as he thought.
One interesting plot twist could be that a character thought to be an enemy turns out to be a long - lost ally. Maybe a cursed book reveals a prophecy that changes everyone's perception of the character's true nature.
A great plot twist could be that Percy Jackson discovers he has a connection to the God of War universe that he never knew about. Maybe one of his ancestors was from that world and it gives him some unexpected powers or abilities. For example, he could suddenly be able to use some of Kratos' signature weapons in a new way.
One interesting plot twist could be a character who was thought to be an enemy turns out to be a secret ally. For example, a minor god who was initially seen as working against the demigods actually has a hidden agenda to protect them from a greater threat that the main Olympians are unaware of.
Perhaps a plot twist where Percy discovers that his own powers are somehow linked to the Bane in a way he never expected. Like his ability to control water is actually being manipulated by the Bane to cause chaos in the ocean realm, which would put him in a really difficult position of having to figure out how to break that connection while still using his powers.
One common plot twist could be Percy discovering that his connection to Artemis brings some unforeseen powers. For example, he might gain the ability to communicate with certain animals that are sacred to Artemis. Another could be that there's a prophecy about him that was hidden until a crucial moment, changing the course of his journey. Or perhaps he finds out that his parentage is more complex than he thought, with some dark secret related to Artemis that others have been hiding.