A new student at school could become Percy's ally. This new student might not be influenced by the existing social hierarchy and could see Percy for who he really is. They could bond over shared interests like reading or video games. Together, they could form a united front against the bullies. In the fanfiction, the new student could be from a different town and have a different perspective on things, which would be helpful for Percy.
His older siblings, if he has any in the fanfiction. They could use their age and influence to protect Percy. Older siblings often have a natural instinct to look out for their younger ones. They could walk Percy to and from school, or have a word with the bullies to scare them off.
It could be some of the more aggressive monster characters. For example, the dog monsters might be territorial and see Frisk as an intruder, so they bully Frisk.
She could make new allies among the female characters who might be more inclined to help her now that she's a girl. For example, some of the female demigods who previously didn't interact much with Percy could now become her friends and allies.
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.
Bob the Titan could potentially be an ally. Since he has some knowledge of Tartarus and has shown kindness before, he might come to Percy's aid again. He could help Percy navigate the dangerous areas and avoid some of the more powerful threats in Tartarus.
Frank Zhang could also be an ally. He is a Roman demigod with shape - shifting abilities. His strength and loyalty would make him a valuable teammate for Percy. Additionally, Nico di Angelo, who has ties to both the Greek and Roman worlds, could be an important ally. His knowledge of the Underworld and his ability to shadow - travel could help Percy in various situations, whether it's getting information or quickly moving around in the Roman camp.
Annabeth would definitely be one of his top allies. She's been with Percy through many adventures and her intelligence would be crucial in helping Percy understand his connection to the creator and any new situations that arise. For example, she could research ancient texts to find clues about the creator's intentions for Percy.
Nico di Angelo could be a great ally. Since he has his own connection to the Underworld, he might understand Percy's new situation better. Another could be Thalia, as she's always been a strong and loyal friend. She would likely stand by Percy despite his new dark powers. Also, Grover could be an ally. His empathy and loyalty would make him support Percy no matter what.
One way could be for Percy to find a group of true friends who can support him. They can stand up to the bullies together. For example, if there are some nice classmates, Percy can join them during breaks and lunches, and the bullies might be less likely to target him when he's in a group.
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.