Maybe Neville could be a central figure. He has always been strong and determined. In a post - apocalyptic world, his skills in Herbology could be extremely valuable. He could be in charge of finding or creating new plants that can provide food, medicine, or protection against the new threats in the world.
A new generation of wizards and witches could be the main characters. For example, the children of Harry and his friends. They could inherit the legacies of their parents and at the same time, carve out their own identities as they struggle to survive and rebuild in a world that has been turned upside down.
Luna Lovegood could be a main focus. Her unique perspective on magic could be used to discover new magical phenomena that emerged after the battle. She might also be helping the other students deal with their post - battle stress, using her calm and dreamy nature to soothe them.
One great post apocalyptic Harry Potter fanfiction is 'The Shattered World'. It presents a dark and desolate world after a magical cataclysm. The characters have to fight for survival in a way that's very different from the original series. Another one is 'Surviving the Ruins' which focuses on how the Hogwarts students band together against new and terrifying threats.
Perhaps a group of radical wizards who believe that the apocalypse was a sign that the old ways of the wizarding world were wrong. They want to create a new order, even if it means using cruel and unethical magic. They see the more traditional wizards, like those who were friends with Harry Potter, as enemies who are holding back progress.
One interesting concept could be the rebuilding of Hogwarts. After an apocalyptic event, the once - great school might be in ruins. The remaining wizards and witches could come together to restore it, using their magic in creative ways. They might have to find new sources of magical energy or deal with dark magic that has been unleashed during the apocalypse.
Hermione could be a main character. As a very intelligent witch, she might assist Harry in his teaching, like helping him prepare complex lessons or providing additional knowledge to the students. For example, when Harry is teaching about ancient spells, Hermione could offer insights from the books she has read.
Hermione could be one. She could come to Degrassi to help Harry. She'd be really good at handling the academic side of things there, like helping students with their studies. And also, she could use her magic knowledge to figure out any magical mysteries.
In post apocalyptic Harry Potter fanfiction, a common theme is the breakdown of the old order. Hogwarts might no longer be the safe haven it once was, and the Ministry of Magic could be in ruins. This forces the characters to create new systems and ways of living. Another theme is the discovery of new powers or abilities. With the world in chaos, some characters may find hidden strengths within themselves that they never knew existed before, which helps them in their fight for survival.
Neville Longbottom could be a main character. He has always had the potential for great things and in a world without Harry, he would be likely to step into the spotlight. He has the courage and the connection to Hogwarts that could make him a central figure in the fight against evil.
Definitely Sam and Dean Winchester. They would be like his surrogate brothers or mentors. Then there's Castiel, the angel. He could have some interesting interactions with Harry, perhaps being intrigued by his magic. Bobby Singer could also be there, guiding Harry in the ways of hunting.