Another possible main character could be a rival collector. They compete with the main collector for the rarest and most valuable items from the Owl House. This rivalry could create a lot of tension and interesting plot twists, as they both try to outwit each other to get their hands on the most coveted collectibles.
Luz is definitely one of the most written - about characters. She's the main character in the show, so it's natural that she features prominently in fanfics. Amity is also very popular. Her relationship with Luz, whether it's friendship or something more, is a big draw for writers. And Hunter is another character that gets a lot of attention. His complex backstory and character arc make him interesting to write about.
One way is to start fanfiction contests that have specific themes related to the positive aspects of 'The Owl House', such as the exploration of the different magical realms or the development of the characters' personalities. By highlighting these areas, fans are more likely to create positive fanfiction rather than sexual ones. Also, fan communities can promote and share only the positive fanfictions they find, creating a positive cycle.
If it's a crossover with 'Frozen', Elsa would be a great character. Her ice powers could contrast with the warm - themed magic in 'The Owl House' in an interesting way. Anna's adventurous spirit would also fit well into the story. From 'The Legend of Korra', Korra could be included. Her ability to bend multiple elements and her strong - willed personality would make for some exciting interactions with the characters of 'The Owl House'. She could even learn new forms of magic from them.
It's mainly about the adventures in a magical world. There are unique characters, like witches and demons. It shows their relationships and the challenges they face in this strange place.