It could be a long - lost relative of Voldemort who has been hiding in the shadows. They might be more cunning than Voldemort and have a different approach to causing trouble in the wizarding world.
Well, in fanfiction, it's possible that a character who has been bullied or marginalized at Hogwarts could turn into the enemy within. They might feel that the school has failed them and seek revenge. It could also be a character who has been exposed to some dark magic accidentally and is now being controlled by it. A jealous student, perhaps someone envious of Harry's fame, could also be a candidate for the enemy within as they might be willing to side with the real enemies to bring Harry down.
Since it's a fanfiction based on Harry Potter, Harry himself is likely to be one of the main characters. He would probably be the recipient of the greatest gift. Hermione and Ron, his best friends, might also be main characters as they often accompany Harry in his adventures.
I'm not sure specifically as there are many different 'Harry Potter' fanfictions. It could be about Harry receiving an unexpected and great gift that changes his journey in the wizarding world. Maybe it's a magical object or a new friendship that helps him in his fight against Voldemort.
Well, it might involve a new character who secretly opposes Harry. This enemy could be working behind the scenes to undermine Harry's efforts against Voldemort. Maybe they're trying to steal the Philosopher's Stone for their own dark purposes.
The last enemy that Harry Potter and the Deathly Hallows destroyed was death itself. Death was a very important element in the novel because it represented the end of life and the transfer of memories. In Harry Potter's adventures, he must fight against the Deathly Hallows to protect human lives and memories. In the end, Harry achieved victory over death by defeating death itself.
Some fanfictions in 'Harry Potter and the Enemy Within' might explore the idea of a teacher being the enemy within. This teacher could be using their position to manipulate students and events for their own dark purposes. They might be influencing the curriculum to promote the ideals of the enemy within or even trying to recruit students to their side. It could also be interesting if the fanfiction shows how the main characters like Harry, Hermione, and Ron figure out who this teacher is and how they stop their plans.
One interesting aspect could be the unique portrayal of Astoria in this fanfic. Maybe it shows a side of her that is different from the original series, perhaps a more complex personality or a different backstory that makes her an 'enemy' in this particular narrative.
In the 'Harry Potter the enemy astoria fanfic', Astoria's development could be closely tied to the events that make her an 'enemy'. For example, if there's a conflict over a powerful magical artifact, her actions and decisions in relation to that could shape her character. She may become more determined and cunning as she pursues her goals, or she could have a change of heart later on due to some unforeseen circumstances in the story.
The key themes often include rivalry. Since it's about an 'enemy', there's likely to be a strong sense of competition, whether it's for academic achievements at Hogwarts like getting the best grades in Potions or winning the House Cup. And secrecy is another possible theme. The characters might be hiding things from each other, adding to the tension. For example, one character could be hiding their true intentions or a secret ability, which makes the relationship with the 'enemy' even more complex.