Harry Potter is a given. In addition to him, I think there could be other characters from the Harry Potter series who might also make an appearance. From the Charmed side, apart from the Halliwell sisters, characters like Leo Wyatt could be important. Since it's a fanfiction that combines two universes, it might also introduce new characters that are created specifically for this story to bridge the gap between the two worlds. For example, a character who has knowledge of both the magic in the Harry Potter world and the power of the Charmed ones.
The main character is Harry Potter as he is the Master of Death in this fanfiction. Alongside him, we should expect to see Piper, Phoebe, and Paige from Charmed. There could also be some of Harry's friends from Hogwarts like Hermione and Ron, although their roles might be different in this new setting. And who knows, there might be some crossover characters that are a mix of the two universes, perhaps a wizard - witch hybrid with the powers of both worlds.
One interesting concept could be how the idea of being the Master of Death from Harry Potter is incorporated into the Charmed universe. Maybe it involves new magical abilities or a different take on the power of life and death.
Definitely characters from both 'Charmed' and 'Harry Potter'. From 'Harry Potter', Harry, Hermione, and Ron are very likely to be main characters as they are the central figures in the original series. In 'Charmed', the Halliwell sisters, Prue, Piper, and Phoebe, would be prime candidates. Their different powers and personalities would create interesting dynamics when interacting with the 'Harry Potter' characters.
There could also be other characters from the Harry Potter universe like Hermione and Ron. They might be involved in helping Harry navigate this new world of being connected to the Charmed Ones. And from the Charmed side, there could be Leo, their Whitelighter, who might have some interesting interactions with the magical folk from Harry's world.
Often, in such fanfiction, new original characters are introduced. They could be the ones who created the charmed lemon in the first place. But it's also possible that characters like Dumbledore could play a significant role. He might know more about the charmed lemon than he lets on and be guiding the other characters from behind the scenes. Neville could also be a main character, using his skills with plants to take care of the charmed lemon or study it.
Obviously, Harry Potter himself. He's the one who has become the Master of Death. Hermione and Ron would also be important. They'd be there to support Harry, and also to question his new power and the moral implications. Dumbledore might also play a role, perhaps as a guide from beyond the grave, since he was always so interested in the Deathly Hallows and what it means to be the Master of Death.
Hermione would surely be one of the main characters interacting with Harry. She would be both intrigued and cautious about his new status. She might help him research and understand the full implications of being the master of death.
Harry Potter is the central figure. Then, the 'charmed one' which could be a previously unknown character or a new take on an existing character from the Harry Potter universe. There might also be antagonists. Maybe some dark wizards who want to use Harry's connection to the charmed one for their evil purposes. And of course, Dumbledore or other Hogwarts professors might play important roles as they often do in stories related to Harry, guiding him and helping him understand his new situation.
Ron Weasley could be another main character. He would be by Harry's side, providing support and his own brand of wizarding skills. Sometimes, characters like Dumbledore might also play a significant role. Even though he's dead, his wisdom could be passed on to Harry in some way, guiding him as he navigates his role as the Master of Death.
Ron Weasley could be another main character. He might be by Harry's side, providing the loyalty and friendship he always has. In some fanfictions, he could also gain some unique abilities or knowledge related to Harry's new state. And Dumbledore, even in death, might still have an influence. His past knowledge and wisdom could be a guiding force for Harry as he navigates his new immortality and power as the Master of Death.
Yes, there might be. Some creative fanfiction writers like to blend different fictional universes. They could create a story where the concept of 'Harry Potter being the Master of Death' is incorporated into a 'LotR' - themed fanfic. It could be an interesting crossover with unique plotlines.