Perhaps Neville Longbottom could take on this role. He has shown great courage throughout the series. His experiences with loss, like the death of his parents, could lead him down a path where he becomes the apprentice of death, using his newfound powers to protect others and bring a new balance to the wizarding world.
Well, the apprentice Potter themselves is often a central and popular character. They are usually portrayed as young, eager, and full of potential. Then there might be the master potter who teaches the apprentice. This character is often wise and experienced, like an old wizard who has seen it all in the world of pottery - making magic. There could also be other apprentices in the workshop, some of whom might be friends or rivals to the main apprentice.
The apprentice's character development can be shown through their changing views on magic. At first, they might be in awe of Grindelwald's powerful and often dark magic. But as they learn more, they start to see the harm it can cause. For example, if they witness Grindelwald using a spell to harm innocent people, it could make them question their loyalty.
There might be a fanfiction where the apprentice Potter is from a humble background but has an extraordinary talent. They are then noticed by a famous wizard potter who takes them under their wing. This could lead to adventures in different magical lands to find rare materials for their pottery. The apprentice might face challenges like dealing with jealous rivals or dangerous magical creatures guarding the materials they need.
Obviously, Harry Potter himself. And there could be Dumbledore, who might guide Harry in this new path related to Merlin. Also, Hermione and Ron could be there, either helping Harry or being a bit skeptical about this new adventure.
Well, it could be about Harry Potter discovering some long - lost magic that was once taught by Merlin. Maybe he stumbles upon an ancient spellbook or a hidden place where Merlin's teachings are preserved.
Lupin could be a very interesting mentor. He could teach an apprentice about dealing with their own inner demons, as he has his own struggles with being a werewolf. He could also pass on his knowledge of defensive magic and how to use magic in a more practical and street - smart way.
One common theme is the struggle between light and dark. Even as Harry becomes a dark apprentice, there is often an internal battle within him, representing the eternal struggle between good and evil. For example, he might still have some lingering feelings of loyalty towards his friends who are on the side of light.
Harry Potter himself is also very popular. He could be seen as an older, wiser apprentice passing on his knowledge of fighting dark magic to the new generation of students. His adventures against Voldemort give him a lot of experience to share.
The apprentice is obviously one of the main characters. They are likely to be a young wizard or witch with great potential. Then there might be characters representing the different houses of Hogwarts, like a descendant of Gryffindor who is a mentor to the apprentice. There could also be a rival apprentice who has different ideas about the founders' magic.