A centaur - like creature but with the ability to fly. It could be an outcast from its own kind and team up with Percy. It would bring a new dynamic to the group with its unique abilities and backstory.
A young demigod who has the power to communicate with the spirits of the monsters. This character could help Percy understand the motives of the monsters better and maybe find non - violent solutions to some of the conflicts.
An ancient sorcerer who was once an ally of the monsters but now sees the error of his ways. He could offer Percy valuable knowledge about the weaknesses of the monsters, but at the same time, his past might make others in Percy's group suspicious of him.
A shape - shifting creature that can take on the form of any animal. It starts off as an enemy, trying to steal something important from Percy and the Wanderer, but later realizes they are on the same side and becomes an ally. This character could bring a lot of action and mystery to the fanfiction.
A new character could be a mortal who has somehow gained the ability to see through the Mist completely. This mortal is on a mission to expose the world of demigods and the gods themselves. Percy has to either convince this mortal to keep quiet or find a way to make them forget what they've seen, all while dealing with the chaos this person is causing in the demigod world.
A Venator wizard who can manipulate time could be an interesting addition. He could help Percy in his quests by using his time - manipulation powers to gain an advantage. Another could be a half - Venator, half - demigod character who is conflicted about which world to side with.
A new type of sea nymph who has the ability to change the color and texture of water. She could be from a far - off part of the ocean that Percy has never explored. Her appearance could bring new mysteries and adventures for Percy, as she might know secrets about the deep sea that are crucial to the safety of the demigod world.
In a 'Percy son of Hades fanfiction', there are many characters that could be added. For example, Charon, the ferryman of the Underworld. He could play a role in Percy's travels within the Underworld. Persephone could also be an important character. She might be initially suspicious of Percy but then come to see his potential. Additionally, the Erinyes, or the Furies as they are more commonly known, could be added. They could be a source of conflict or assistance for Percy, depending on the situation.
A centaur who has knowledge of ancient prophecies involving both Percy and Artemis could be added. The centaur could act as a guide or a mentor to them during their adventure. He could provide crucial information about the enemies they are facing and how to use their combined powers effectively. For example, he might know of a weakness in a powerful foe that only Percy's unique abilities and Artemis' lunar powers can exploit.
A character could be a young oracle who has visions related to Percy's new adventures. She could be a bit of an enigma, not fully understanding her own powers and sometimes giving cryptic messages that Percy has to decipher. This would add an element of mystery to the story.
There could be a character who is a mentor to Percy in understanding his devilish side. This character might be an ancient being with knowledge of both the divine and the demonic. For example, a fallen angel who has seen the rise and fall of many with such mixed heritages.
There could be a new oracle who is specifically attuned to Percy's 'son of fate' situation. This oracle might be a young demigod with unique powers that help Percy understand his fate better. Maybe they can see visions of the future that are directly related to Percy's journey.
Annabeth could be a likely member as she has a deep connection with Percy already. Another could be Piper, given her charm - speaking abilities and her friendship with Percy. And maybe Hazel, with her unique powers and kind heart.