One aspect that can be explored in Freya and Bell fanfiction is the idea of destiny. Freya believes Bell is destined for great things, and she wants to be a part of that journey. A fanfiction could show how she subtly influences Bell's choices in the dungeon, leading to both growth and conflict. Bell might start to question why certain opportunities seem to present themselves so conveniently, and as he discovers Freya's role, he has to decide whether to accept her help or forge his own path.
One great idea for a Freya and Bell fanfiction could be a story where Freya, in her guise as a normal citizen, befriends Bell without him knowing her true identity. They could go on adventures in the dungeon together, and Bell would unknowingly start to develop feelings for this mysterious woman, all while Freya struggles with her own powerful and possessive love for him.
Yes, there are quite a few. You can start by looking on fanfiction websites like Archive of Our Own. Some fanfictions might explore Bell's fear in relation to his complex relationship with Hestia, perhaps due to her over - protectiveness or his own insecurities in the face of her expectations.