Story Idea
Demons are real and very dangerous, but can be captured and contained through complicated magic circles, mandalas, or sigils that let mages bind them and tap into their power.
For a long time, everybody assumed that the bigger the circle, the more powerful it was... but a math nerd, who is not actually a mage, figures out that it's not the AREA of the magic circle that determines the power, it's the BOUNDARY - the length of the outside-most edge.
Using this knowledge, he captures one of the most powerful demons in the world... using the Mandelbrot Set, since the boundary for one of those is technically infinite.
Now, he has accidentally become a mage because he has an incredibly powerful demon bound to him, and he's going to go wreck the magic world by using maths and logic to decode and modernize their whole bullshit.
It's like Harry Potter and the Methods of Rationality, but without the TERF lady being involved and hopefully no AI Death Cults either.