Perhaps there's a group of other elemental controllers who see Percy as an equal. They might team up with him to fight against a common enemy. For example, a fire - controller could help Percy in a situation where he needs heat as well as water control. They would complement each other's powers and form a strong alliance.
Annabeth Chase would likely be one of his main allies. She's smart and resourceful, and she could help Percy figure out how to use his space - controlling powers in the best way, like strategizing how to navigate through a dangerous part of space.
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.
In the fanfiction, Percy's water - controlling ability might be the key to solving a mystery. Say there's a strange drought in the land, and Percy uses his power to figure out what's causing it. He might discover that there's an evil force sucking up all the water, and then he has to use his ability to fight against this force. This would not only involve his power but also his courage and intelligence, making the plot more complex and interesting.
Grover might also be an ally. His connection to nature could be useful in Percy's new role. For example, he could help Percy understand any nature - related aspects of Olympus or deal with nature spirits in the realm. Also, some of the more benevolent gods like Poseidon (Percy's father) and Athena (Annabeth's mother) might side with Percy, at least to some extent, as they have their own interests in seeing Percy succeed in maintaining order in Olympus.
Annabeth could be a strong ally. She's smart and has always been by Percy's side. Her knowledge and strategic thinking would be invaluable when Percy is dealing with the new aspects of his primordial powers.
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.
There might also be a lost spirit or a demigod who was previously trapped in Tartarus and has managed to survive. This character could share their experiences and skills with Percy, and together they could try to find a way out or at least make the best of their situation in Tartarus.
He could have some primordial entities as allies. Maybe Erebus, as it is also related to the more chaotic and ancient aspects of the world. Another possible ally might be some minor chaos spirits that recognize his special status.
Annabeth could be a great ally. Her intelligence and strategic thinking would be very useful in dealing with the chaos Percy often gets into. She could help him plan his moves and figure out the motives of chaotic enemies.
Annabeth could be a strong ally. She has always been there for Percy, and even though his parentage has changed, her loyalty might still hold. Grover too. He's Percy's best friend and would likely stand by him no matter what. Another potential ally could be the Hunters of Artemis. Since Diana is another name for Artemis, they might see Percy as someone they need to protect and help, especially if he is involved in something that concerns the goddess.