Maybe there will be a competition or a test in the DADA class that Harry is teaching. Tom could either shine or struggle, and this could affect his relationship with Harry. If he does well, he might gain more respect for Harry and DADA. If not, he could become determined to improve.
It's possible that Harry discovers some hidden talent in Tom for DADA. This could lead to a special training arc where Harry focuses on developing Tom's unique skills. As a result, Tom could become a protege of sorts, and this new relationship could have far - reaching implications for the fanfiction's plot, such as changing the way other characters view Tom.
Well, it could be that Harry's hands - on experiences from his own time at Hogwarts make his teaching really engaging. He might share his encounters with dark creatures and how he overcame them. This could make Tom more aware of the practical side of DADA.
For Harry, he could become more confident in his teaching abilities. He has always been a learner, but now he has to be the one imparting knowledge. The Marauders might develop a new respect for the importance of DADA. For instance, Sirius might see it as more than just a subject to goof around in. Remus could gain new insights into teaching methods that he can later use when he becomes a teacher himself at Hogwarts.
One possible plot development could be that Harry uses his wits and some hidden magic skills to try and escape. For example, he might remember a spell he learned from Dumbledore in a previous encounter that could temporarily stun Tom Riddle, giving him a chance to run. Another development could be that his friends, like Hermione and Ron, figure out where he is and come to his rescue. They could use the Marauder's Map or some other magical device to track him down. There could also be a situation where Tom Riddle has a change of heart during the kidnapping, perhaps due to some long - forgotten memory that Harry triggers, and he decides to let Harry go, but not without some sort of warning or cryptic message about the future.
As the teaching progresses, they could develop a sort of mentor - mentee relationship. Harry would be constantly trying to steer Tom away from the Dark Arts, while Tom would be trying to learn as much as he can from Harry. However, there would always be an underlying tension because of Tom's future as Voldemort. Their relationship might be a complex dance of trust and suspicion.
One possible plot could be that Harry, using his knowledge of love and friendship, tries to teach Tom about the power of positive emotions. He might show Tom how his own journey was shaped by the love of his friends and family, in contrast to Tom's more solitary and power - hungry path. Maybe Harry takes Tom to Hogwarts in a time - travel like scenario and shows him the true meaning of the houses, not just the pursuit of power within Slytherin.
In this fanfiction, Harry teaching DADA could lead to some really creative storylines. He might invite some of his old friends, like Hermione or Ron, as guest lecturers. They could share their own knowledge and experiences, which would add a lot of variety to the classes. Also, Harry could start some sort of mentorship program for students who show a particular aptitude in DADA.
One possible plotline could be that Harry, with his knowledge of the Dark Arts from his own experiences, tries to show Tom the true nature of defensive magic. He might start by teaching basic spells like the Shield Charm. Harry could also share his insights on how to resist the allure of the Dark Arts, which is something Tom struggles with in his later years as Voldemort.
Perhaps in the 'harry is the heir of pendragon fanfiction', Harry's new status as the heir of Pendragon causes a stir in the wizarding world. Some might fear his new - found power, while others might see him as a great hope. He could be drawn into a political struggle within the magical community as a result.
Well, one possible plot development could be that Harry learns some really unique combat skills from Scathach. Maybe he becomes a much more formidable wizard in dueling. Another could be that he gains a different perspective on magic through her teachings, which helps him in his battles against Voldemort.
One possible plot development could be that Voldemort fully regains his power without Harry as an obstacle. The wizarding world would be plunged into complete darkness. His friends, like Hermione and Ron, might go into a deep state of despair and then form a resistance group. They would try to find other ways to defeat Voldemort, perhaps by seeking out more powerful magical artifacts or uniting with some previously neutral magical creatures.