You know, some of the interesting parts are when the Doctor uses his TARDIS to visit Hogwarts or when Harry Potter discovers a Time Lord artifact that changes the course of events. Fanfiction writers get really creative with these concepts!
There are all sorts of fanfictions. Some might focus on crossovers where characters from both universes meet and interact. Others could explore alternate timelines or what-if scenarios.
Well, 'The Magic of the TARDIS' is a well-known crossover. It combines the magical world of Harry Potter with the adventures of the Doctor in really interesting ways. The characters' interactions and the plot twists make it a great read.
Often in such fanfictions, you'll find crossovers where the Doctor helps solve magical mysteries in the Harry Potter world. Another interesting aspect could be seeing how magic interacts with the Doctor's time and space technology.
The story could have all sorts of twists and turns. Maybe Harry uses his newfound power as the Master to shape the wizarding and Time Lord worlds in unexpected ways.
In this kind of fanfiction, the main antagonists could be a combination of the traditional Harry Potter villains like the Death Eaters and new threats from the Marvel side. For instance, Dormammu could somehow sense Harry's potential and try to either possess him or destroy him to prevent him from becoming a powerful force against him. And of course, there would always be some wizards in the Harry Potter world who are against any kind of change or outside influence, and they could also oppose Harry.