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.
Power and its corrupting influence is also a theme. Tom Riddle's thirst for power led him to become Voldemort. Fanfictions may show how Iris Black is either tempted by the same power or how she resists it. Harry Potter, having faced Voldemort's power, serves as a contrast in these stories. For example, in some fanfictions, Iris Black discovers a new type of magic related to Tom Riddle's early experiments, and she has to decide whether to use it for good or be corrupted like Riddle.
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.
One interesting fanfiction could be where Iris Black has some sort of connection to Tom Riddle's past that Harry Potter discovers. For example, she might be related to one of Riddle's early victims and through her, Harry uncovers new secrets about Voldemort's (Tom Riddle) rise to power.
One common theme is the exploration of good and evil. Since Tom Riddle becomes Voldemort, fanfictions often examine how Harry, as the symbol of good, could influence or be influenced by Tom. Another theme is the power of magic. Writers like to play with different magical concepts and how they might be used by Harry and Tom.
Another theme is redemption. Some fanfics explore the possibility of Tom Riddle being redeemed, perhaps through his interactions with Harry. It's an interesting concept as it goes against the established view of Voldemort as an irredeemable villain. These stories usually dig deep into Tom's past and what led him to become so evil in the first place, and then show how Harry's influence could potentially change his path.
One common theme is the exploration of Tom Riddle's fall to the dark side. How Harry might interact with him during different stages of that transformation. For instance, some fics might show Harry trying to prevent Tom from becoming Voldemort.
One great Tom Riddle fanfiction is 'The Heir of Slytherin's Redemption'. It delves into the idea of Tom Riddle having a change of heart. Another is 'Tom Riddle: The Lost Years' which explores what he might have been up to during the time not fully covered in the original books. And 'Riddle's Unraveling' is also good as it shows different perspectives on his fall to the dark side.
A good old fanfiction could be the one where Tom Riddle's relationship with the Chamber of Secrets is explored in more detail. It might show how he found out about it and his early experiments with the Basilisk. This could give a new perspective on the events in the original books.
Another theme is the exploration of power dynamics. Harry has his own power, and Tom is extremely powerful in a different way. Their relationship in the fanfictions often explores how these different powers interact and whether they can find a balance in their romantic relationship. For example, in some stories, their combined powers are seen as a way to overcome greater threats in the wizarding world.
One common theme could be the exploration of an unexpected relationship between Harry and Tom. Since it's mpreg involved, it might also deal with themes of new life and how it changes their dynamic. Another theme could be the blurring of the lines between good and evil as they are brought together in this very different situation.
One common theme is the exploration of redemption. It often shows Tom Riddle in a different light, as if Harry's presence could potentially lead to his redemption. For example, in some fanfics, Harry's kindness and understanding start to break down Tom's dark barriers.