Who could be the main antagonists in a 'Percy and Reyna get married' fanfiction?

One possible plot could be that after years of adventures and growing closer as friends, Percy and Reyna start to realize they have deeper feelings for each other. They might face some initial resistance from their friends who are used to them just being comrades. But as they work together on a new mission, their bond strengthens and they finally decide to get married. The wedding could be a grand affair with all their demigod friends in attendance, celebrating their union.

Some ancient and powerful monsters could be antagonists. Since Percy is now connected to the Fates, any disruption in the natural order might attract these monsters. They could see the situation as a chance to gain power or revenge. For instance, a powerful Titan who was once imprisoned might see Percy's new status as a way to get back at the gods by attacking him.

One common antagonist could be an old enemy of Artemis who doesn't approve of her marrying Percy. This enemy might be a powerful Titan who sees their union as a threat to his plans for revenge against the gods.

It could be the navy. They see pirates as outlaws and would be determined to capture Percy and his crew. They might have better - equipped ships and more trained soldiers, making them a formidable foe for Percy and his fellow pirates.

Monsters could also be antagonists. With Percy in a new, more powerful state as a godling, there could be new and more powerful monsters that are drawn to his power. These monsters might be stronger and more intelligent than the ones he faced as a demigod, and they could be after his godly essence or trying to use him for their own dark purposes.

A powerful sorcerer who wants to use Percy for his own dark purposes could be an antagonist. This sorcerer might see Percy's unique abilities as a key to unlocking some sort of forbidden magic.

It could be an old enemy of the gods who has been biding their time. Maybe a powerful Titan that was thought to be defeated but has found a way to come back. This Titan could use Percy to kidnap Reyna because she has a connection to a certain power that the Titan wants to use to regain full strength and overthrow the gods once again.

The priesthood of an ancient Egyptian cult that has been forgotten but still has some lingering power could be antagonists. They believe that the union of Sadie and Anubis is against the old ways and will bring bad luck or some sort of cataclysm. They might use dark magic to try and separate Sadie and Anubis. Also, there could be a jealous god or goddess, perhaps Isis, who is used to being in a position of power and influence. She might see Sadie as a threat to her status, especially if Sadie's relationship with Anubis gives her some sort of special powers or influence in the divine realm.

The Black Organization could still be a major antagonist. Even though Shinichi and Ran are married, the Organization might try to target Shinichi because of his knowledge of their secrets. They could try to use Ran as a way to get to Shinichi, which would create a lot of tension in the story.

It could be an ex - partner of either Yuno or Yuki. For example, if Yuno had a really possessive ex, that person might try to break up their marriage out of jealousy. They could spread false rumors or create misunderstandings between Yuno and Yuki.