In Harry Potter fanfic, a faery hero could be a character with magical faery abilities who uses them to fight dark forces. For example, a faery who can manipulate time and space to outwit Voldemort's minions. They might also use their natural charm and allure to deceive the enemy, like luring Death Eaters into a trap with their faery magic.
There are likely to be. Since fanfiction is a vast and diverse realm, it's quite possible for someone to have written about faery heroes in relation to Harry Potter. These faery heroes could be from a hidden part of the wizarding world, with their own culture and magic that intersects with the main story of Harry Potter.
They can be incorporated as new magical creatures in the Forbidden Forest. Maybe they have their own hidden enclaves there and interact with Hogwarts students who stumble upon them. For instance, a faery hero could offer help to a lost student by using its faery magic to guide them back to the castle.
They can be introduced as allies. For example, they could come to Hogwarts when they sense the dark forces rising. Their faery magic could be different from the regular wizarding magic, like being able to control nature in ways wizards can't. This would make them valuable in battles.
Well, a 'bad faery fanfic' could be about a faery that has a negative or evil nature. It might involve the faery causing trouble in a fictional world, like playing tricks on humans or other magical creatures.
Obviously, Harry Potter himself is a likely hero. His experience in fighting Voldemort has given him the skills and courage to face new apocalyptic threats. Hermione Granger is also a strong candidate. Her intelligence and vast knowledge of magic would be invaluable in trying to solve the problems causing the apocalypse. Ron Weasley, with his loyalty and ability to think on his feet, would be right there beside them, fighting against whatever doom is approaching.
Hermione Granger would also be a main character. Her intelligence and vast knowledge of magic would be invaluable in any situation the heroes face. She could come up with strategies and solutions.
One interesting plot could be the heroes from different Hogwarts houses uniting against a new dark wizard threat that is more powerful than Voldemort. They might have to combine their unique magical skills and knowledge.
You could try looking on fanfiction websites like Archive of Our Own. There are often various types of fanfics there, and you might be able to find 'bad faery fanfic' among the fantasy - related works.
Well, just based on that title alone, it's difficult to determine its quality. There are so many aspects that make a Harry Potter fanfic great. For example, it could explore new relationships between the characters, or create exciting new magical adventures. But we don't know if 'skull is harry potter fanfic' does any of those things. So, it might be good, it might not.