Love and conflict are often common themes. Their relationship might be filled with love but also face various conflicts, either from external forces or their own internal struggles.
The theme of discovery is quite common. The reader is constantly discovering new things about Trigon, his motives, his world, etc. And there's also the theme of survival. Given Trigon's nature, the reader often has to find ways to survive in the situations they are in. This could involve outsmarting Trigon or finding allies within his realm.
He may also try to talk his way out. Nightwing is known for his charm and intelligence. He could try to reason with Slade, find some common ground, or play on Slade's emotions. Maybe he could remind Slade of a past event where they had a moment of mutual respect, hoping to make Slade let him go.
One possible motive could be revenge. Maybe Nightwing has thwarted Slade's plans in the past, and Slade wants to get back at him. Another could be that Slade sees Nightwing as a valuable asset. He might plan to use Nightwing's skills for his own evil purposes, like forcing him to steal something or gather information for him.
Some of the dark wizards who are looking for a new source of power might target Harry. They might think that by capturing or controlling him, they can access the powers of Trigon. There could also be entities in other dimensions that see Harry as a key to opening portals between worlds and want to use him for their own malicious purposes.
Well, one possibility could be that Harry has to deal with the dark and chaotic powers inherited from Trigon. He might struggle to control these powers while also facing the threats in the wizarding world. Maybe he discovers a new form of magic related to Trigon's realm.
The blend can occur through the use of magic in relation to trigonometry in solving problems. For example, in a fanfiction, a magical creature is lost in a forest that is magically generated with trigonometric patterns. The characters need to use their knowledge of both magic and trigonometry to find the creature. Also, a character's magical power could be related to their understanding of trigonometry, so as they learn more math, their magic becomes stronger and more versatile.
There could be a fanfiction where the Triwizard Tournament tasks are influenced by trigonometry. For instance, in one task, the champions have to navigate through a maze that is constantly changing its shape based on trigonometric equations. They need to calculate the right angles and paths to get to the center. Also, a character could be a math prodigy in the Muggle world who discovers they have magic and tries to combine their knowledge of trigonometry with spells at Hogwarts, creating a whole new approach to magic that others are both amazed and skeptical about.
Jessa Slade in Fantastic Fiction is probably a writer with her own unique style. In Fantastic Fiction, there are various sub - genres like high fantasy, urban fantasy etc. She might be known for her take on one of these. Maybe she has a series of books with a particular set of characters that have captured the attention of readers in the Fantastic Fiction community.