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.
In certain fanfictions, Iris Black could be a time - traveling character. She goes back in time and witnesses Tom Riddle's transformation into Voldemort. Through her interactions with the younger Tom Riddle, she tries to change the course of history. Harry Potter then gets involved when he discovers Iris's time - traveling adventures and they work together to stop Voldemort before he becomes too powerful.
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 great 'Harry Potter Tom Riddle Fanfiction' is 'The Heir of Slytherin's Redemption'. It shows a different side of Tom Riddle, exploring what could have happened if he had been given a chance at a different path. It has a really interesting plot that keeps you hooked from start to finish.
One great fanfiction is 'The Boy Who Lived Again'. It explores an alternate universe where Harry and Tom Riddle have to work together to save Hogwarts from a new dark threat. The author does an amazing job of portraying their complex relationship.
One great fem dark Harry Potter and Tom Riddle fanfiction is 'The Darker Path'. In this story, the female Harry Potter character has a complex relationship with Tom Riddle. The author does an amazing job of exploring the darker aspects of the wizarding world. It shows how the two characters interact in a world that's more morally gray than the original series. Another one could be 'Shadows of the Dark Lord'. Here, the fem Harry is a powerful force against Tom Riddle's schemes, but also has her own inner demons to battle.
One interesting fanfiction could be one where Barty Crouch Jr is forced to team up with Harry Potter against Tom Riddle's resurging threat. Maybe in a scenario where Voldemort (Tom Riddle) has found a new way to gain power and Barty Crouch Jr, who has a complex history with the Death Eaters, has to side with Harry to save the wizarding world.
A popular one is 'Soulmate Bonds in the Wizarding World'. In this fanfic, the fem Harry Potter's journey with Tom Riddle as her soulmate is filled with challenges. It shows how the two characters, who are so different in nature, try to come to terms with their soulmate status. It also has some interesting sub - plots involving other Hogwarts students and their reactions to this unusual pairing.
One popular idea in such fanfiction could be that Harry, through some magical time - turning or alternate reality scenario, discovers Tom Riddle before he fully becomes Voldemort. Harry might see the good in Tom that was lost over time and tries to prevent his fall to the dark side. Their soulmate connection could be a powerful force that draws them together, even as their destinies seem so opposed.
One popular type of fanfiction in this vein could be about Tom Riddle's interaction with magical creatures during his time at Hogwarts. Maybe he discovers a creature that has some connection to the dark arts and tries to use it for his own gain. For example, he might come across a basilisk in the Chamber of Secrets earlier than in the original story and attempt to control it to intimidate other students.
An old Harry Potter fanfiction about Tom Riddle could be about his time as a young wizard trying to gain followers. He was a very intelligent and manipulative character. Fanfictions might explore how he used his charm and intelligence to persuade other students to his way of thinking. Maybe he starts a secret club where they study dark magic together, which is a precursor to his later Death Eaters.
One great 'Harry Potter and Tom Riddle' fanfic is 'The Boy Who Lived' (assuming there is one with this title in the relevant category). It might explore an alternate relationship between Harry and Tom. Another could be 'Riddle's Heir' which might delve into the idea of Harry having some connection to Tom Riddle's legacy in a new and exciting way. And 'Harry and Tom: A Different Path' could show how their destinies could be intertwined in a unique plotline.