Well, it could be that Dumbledore, in some fanfic versions, figures it out first and then reveals it to Harry. Dumbledore is often portrayed as having a deep understanding of magic. He might have noticed some strange magical patterns or behaviors related to Harry that led him to suspect and then confirm that Harry was a Horcrux. And then he would tell Harry about it, which is how Harry comes to know.
In fanfic, it could be through a dark spell gone wrong. Maybe a spell that was meant to destroy the Horcrux instead backfired and caused it to merge with Harry.
Well, in some fanfictions, a Horcrux might be purified through powerful magic spells that are specifically created for the purpose. For example, a spell that can reverse the dark magic used to create the Horcrux in the first place.
The Horcrux Fragment of Hero Island was an item that could be purchased in the Horcrux Shop to exchange for a Horcrux. The method of obtaining a Horcrux fragment may vary depending on the game version, but it can usually be obtained by completing specific missions, challenging or defeating specific enemies.
Horcrux fragments can be exchanged for different types of Horcruxes, including ordinary Horcruxes, advanced Horcruxes, and bound Horcruxes. Normal Horcruxes were not bound, while high-level Horcruxes and bound Horcruxes were bound and could only be traded with specific NPCs or purchased with game currency.
The process of exchanging Horcrux fragments for Horcruxes may face challenges and risks such as being defeated by enemies, encountering random events, and so on. Therefore, when exchanging for Horcruxes, it was recommended that players possess sufficient strength and skills to ensure that they could exchange for the Horcruxes they desired.
In some fanfictions, Draco might use his knowledge of the Dark Arts and Hogwarts' secrets. Since he was raised in a Death Eater family, he could have insights into how Voldemort might have hidden the Horcruxes. For example, he might know of certain places within the school that Voldemort frequented or had an interest in.
In many fanfiction works, Hermione being a Horcrux is a fascinating concept. It gives a whole new dimension to the story. By making Hermione a Horcrux, it creates a complex situation. The other characters would have to deal with the fact that she is not only their friend but also a container of a part of Voldemort's soul. This could change the dynamics of their relationships. It also opens up possibilities for new magical solutions to defeat Voldemort, as they would have to find a way to destroy the Horcrux within Hermione without harming her.
If Harry were to create a Horcrux in fanfiction, it would likely lead to a great corruption of his soul. Horcruxes are dark magic, and the act goes against all that Harry stands for in the original series. He might start to show signs of increased aggression, a detachment from his friends, and a growing attraction to the Dark Arts.
In some fanfictions, Draco might use his knowledge of the Dark Arts. He could have insights into the protections around the cave that Voldemort might have set up, given his family's closeness to the Dark Lord. For example, he might know about certain spells or enchantments that are typical of Dark magic and be able to help the characters navigate through them.