Who could be the main antagonist in a Percy Jackson Phoenix King fanfiction?

The main antagonist could be a primordial being that has been awakened. It sees the phoenix as a threat to its existence because the phoenix represents rebirth and renewal, which goes against the primordial being's nature of chaos and destruction. So, it tries to destroy the phoenix and Percy has to protect it, along with his friends, using all their skills and the unique powers they possess.

It could be a powerful sorcerer who wants to control the Hellhound King for his own evil purposes. This sorcerer might be trying to use the Hellhound King's strength to take over Camp Half - Blood or other important places in the Percy Jackson world.

It could be an ancient and powerful dragon that has been awakened by the arrival of Percy in Alagaesia. The dragon might see Percy as a threat to its rule or territory and decides to go after him. This dragon could also have some special abilities that make it difficult for Percy to defeat, like being able to nullify his water powers for a short time.

A powerful Titan who wants to use the Hellhounds for his own evil purposes could be the main antagonist. He might try to capture Percy and force him to command the Hellhounds to do his bidding, like attacking the demigod camps.

Maybe it's a corrupted dwarf. This dwarf once served the 'King under the Mountain' but has been swayed by dark magic. He wants to take over the kingdom and is willing to do anything to achieve his goal. He would be a dangerous foe as he knows all the secrets of the mountain and has some dwarven magic at his disposal.

The obvious choice for the main antagonist could be a powerful and ancient monster who has the ambition to be the king of all monsters. It could be a Titan - like creature that has been in hiding for centuries, gathering strength. Maybe it's a monster that was once defeated by the gods but has now returned stronger than ever.

It could be a power - hungry Atlantean noble who wants to rule not just Atlantis but also the surface world. He sees Percy as a threat to his plans and tries to stop him at every turn.

A new and powerful demon that has emerged from the darkest corners of the underworld. This demon is bent on using Percy's connection to the overworld to break through the barriers between the two worlds and unleash chaos. It has powers that are different from what Percy has faced before, like the ability to manipulate the very essence of the underworld's environment.

A powerful Amazonian sorceress who has turned against her own kind and is now trying to use dark magic to take over the world. She could see Percy as an obstacle in her path and constantly try to defeat him.

Maybe it could be a demigod who has become obsessed with power through gaming. This demigod, let's say a child of Hades, discovers a way to use dark magic and combine it with gaming technology to try and rule over all the other demigods. He sees Percy as a major threat to his plans because Percy is so popular and has strong powers, so he constantly tries to undermine Percy at every turn.