Another theme is the exploration of identity. Tom has to re - evaluate who he is when he is placed in a new family. He might struggle with his past self and the new identity being thrust upon him by his adoptive family and their values.
One common theme is redemption. When Tom is adopted, the new family often tries to steer him away from his future as Voldemort, offering a chance at redemption. For example, they might introduce him to positive values and relationships.
Family and heritage play a big role. She has to deal with the fact that her father is one of the most feared wizards in history. There's often a theme of secrecy as well. She might have to keep her true identity a secret from her friends. Also, power is a theme. As Tom Riddle was powerful, she may inherit some of that power and has to decide how to use it, for good or evil.
Another theme is redemption. Some fanfictions try to show Tom Riddle's possible redemption through his relationship with fem Harry. They might explore how her presence and influence could change his path towards the dark side. It's an interesting concept as it gives a new perspective on the character of Tom Riddle.
Well, a frequent theme is the exploration of family. Harry has always been an orphan, and suddenly finding out he's Tom Riddle's son would completely redefine his understanding of family. There could also be themes related to the battle between good and evil within himself. Since he has the blood of a dark wizard, he may have to constantly fight against his darker instincts. Also, the theme of acceptance by the wizarding world could be present, as they may be hesitant to accept someone with such a dark heritage.
His relationship with other characters is also a common theme. For example, how he interacts with Dumbledore or his classmates at Hogwarts. Some fanfictions also focus on his inner turmoil, the conflict between his human side and the dark side that is growing within him.
Power is a frequently seen theme in tom riddle fanfic. Since Tom was always so obsessed with power in the original story, fanfics expand on this, showing how he might gain or lose power in different situations. Love is also a theme sometimes. It's interesting to see how love could potentially change Tom Riddle, as he was not really associated with it in the main series.
A common theme is mystery. Since Tom Riddle is such a mysterious character, fanfictions often explore the secrets of his past that Iris Black might be related to. Harry Potter, being the main character in the original series, is usually the one to unravel these mysteries.
One common theme is the battle between good and evil. Since Harry represents good and Tom Riddle is the symbol of evil in the original series, fanfics often explore this dichotomy further. For example, how Harry tries to prevent Riddle from doing more harm.
One common theme is power struggle. Tom Riddle often has a thirst for power, and when he crosses over into other worlds or stories, he may face new challenges or rivals for power. Another theme is the clash of cultures. His own dark and calculating nature from the Harry Potter universe may contrast with the values and norms of the new world he enters. And identity exploration can also be a theme. As he experiences new things, he might question who he really is.
Power is a common theme. Since Tom Riddle is already a power - hungry character in the original lore, as a vampire, his pursuit of power becomes even more complex and dangerous.
Power struggle is also quite prevalent. The OC often has some sort of power or knowledge that either challenges or complements Tom Riddle's own power. For example, the OC could be a seer, and their visions of the future clash with Riddle's plans. This creates a tense dynamic throughout the story.