Grover Underwood could also be included. His connection to nature as a satyr could be really interesting when placed in the magical and somewhat gloomy setting of Grimmauld Place. And Harry Potter, of course. His experience with fighting dark forces and his status as the Boy Who Lived would make for some great storylines when combined with the demigods from Percy Jackson's world.
Annabeth Chase from Percy Jackson's world. She could bring her strategic mind to Grimmauld Place. And Sirius Black would be a fascinating character to include. He has his own complex backstory in the wizarding world, and his interactions with the demigods could be really exciting, especially considering his rebellious nature.
One of the most interesting characters to include would be Hermione from Harry Potter. Her intelligence and knowledge of magic could help Percy and his friends in many situations. Also, Captain America from the Avengers. His leadership and sense of justice would blend well with Percy's own heroic nature. And Clary from the Mortal Instruments, her skills as a shadowhunter and Percy's demigod abilities could create a really engaging story.
One idea could be that Percy Jackson gets lost and somehow ends up at Grimmauld Place. There, he discovers some magical artifacts that have a connection to the Greek gods. Maybe the magic in Grimmauld Place reacts strangely to his demigod powers.
Obviously, Percy Jackson and Carter Kane themselves are the most essential characters. Their different personalities and powers would create a great dynamic. Percy with his ability to control water and his quick - wittedness, and Carter with his skills in Egyptian magic. Annabeth Chase from Percy's world would also be interesting. Her strategic mind could help in planning against the combined threats. And from Carter's side, Sadie Kane could add a lot. Her sass and powerful magic would make her a force to be reckoned with. Plus, the interactions between Annabeth and Sadie would be really fun to write.
Definitely Percy and Artemis themselves. Percy with his demigod powers and his ability to adapt to different situations is always interesting. Artemis, being a powerful goddess, adds a lot of depth and mystery. Also, including Chaos as a character can be really cool. It could be this all - powerful, enigmatic being that controls the very essence of disorder. Another interesting character could be one of Percy's friends like Grover. Grover's satyr abilities and his loyalty to Percy could play an interesting role in a story involving Chaos and Artemis.
Definitely Percy, as he is the center of the 'Remember Me' concept. But also, characters like Nico di Angelo could be really interesting. Nico has his own dark past and powers, and he could potentially use his abilities to try and reach into Percy's forgotten memories. Another interesting character would be Chiron. His wisdom and knowledge of the past could be crucial in finding a way to restore Percy's memory. And let's not forget Tyson, Percy's half - brother. His simple - minded but strong and loyal nature could bring some heart - warming moments as he tries to help Percy.
Issei would be really interesting. He's the main character in DxD and has his own set of powers and a rather unique personality. His pervy nature would contrast with Percy's more heroic and sometimes serious demeanor. Their interactions could be both comical and lead to some great character development for both.
Percy himself is a must - include. His adventures and his powers as a son of Poseidon always make for great fanfiction material. Also, Annabeth. Her intelligence and her relationship with Percy add a lot of depth.
Grover can be a great addition. His ability to sense danger and his connection to nature can be translated into some unique in - game abilities. Also, Nico di Angelo is quite popular. His control over the dead could be a very cool power - up or special ability in the fanfiction's gaming world.
Percy himself is obviously a very popular character to include since the whole concept of tg (transformation) can be applied to him in many different and interesting ways. His friends like Annabeth are also popular. You can create scenarios where Annabeth has to deal with Percy's transformation and how it affects their relationship.
Annabeth is also highly popular. Her intelligence and relationship with Percy add a lot of depth to the stories. In fanfiction, she can be involved in solving complex puzzles or leading her own quests.