Neville Longbottom could also play a more prominent role. Neville has his own growth arc in the series, and after Sirius's death, he could bond more with Harry over their shared experiences of loss. They could support each other in their fight against the Dark Arts. And perhaps some of the Death Eaters who were involved in Sirius's death could be main characters from the antagonist side, as Harry tries to track them down and bring them to justice.
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.
Obviously, Harry Potter himself. He would be a central figure as he was the key in the battle against Voldemort. His friends Ron and Hermione would also be important. They've been with him through thick and thin. Neville Longbottom would be another likely main character. His heroics in the final battle would give him a significant role in the post - battle world. Ginny Weasley too, as Harry's girlfriend and a brave witch in her own right.
Obviously, Harry Potter himself would be a main character since the title revolves around him. Hermione and Ron are also very likely to be involved. They are Harry's closest friends throughout the series and would surely play a part in a story where Harry is welcoming death. They might try to stop him or support him depending on the direction of the fanfiction.
Voldemort would remain a major character. Harry's new abilities and perspective from being raised by Death would make their conflict even more complex. Harry might approach the fight against Voldemort with a different strategy, one that is influenced by the teachings of Death.
Ron and Hermione become even more protective of Harry. They are constantly by his side, trying to cheer him up. Their relationship with Harry deepens as they share his pain. In some fanfictions, this brings Ron and Hermione closer together romantically as well, as they bond over their shared concern for Harry.
Well, Harry Potter is the key figure. In the harem, there could be characters like Daphne Greengrass. She is from a pure - blood family and could bring an interesting perspective. Pansy Parkinson could also be a part of it, which would create a lot of drama considering her previous attitude towards Harry. And then there's Tonks, who is a fun and unique character and could be an interesting addition to the harem.
In some fanfictions, Harry becomes more determined to fight against Voldemort. He channels his grief into training harder and becoming a stronger wizard. He often has flashbacks of Sirius which fuel his anger towards the Death Eaters and Voldemort, seeing them as the root cause of his loss.
Definitely Harry, Ron, and Hermione. They were the central characters during the war and would likely continue to be important in the post - war stories. They would be using their skills and experiences to shape the new wizarding world.
Definitely Harry Potter. His death or his experiences after death can open up a lot of storylines. Sirius Black might be a popular character in such fanfictions too. He died quite tragically in the original story, and his return in some form in the afterlife could be really interesting. Luna Lovegood could also be involved. Her unique perspective on life and magic might translate into an interesting role in the afterlife. And Severus Snape, considering his complex character and his ultimate sacrifice, he would be a great addition to explore in the afterlife scenarios.
Well, aside from Harry and Death, his friends like Hermione and Ron could also be important characters. They might try to stop Harry from making the deal or help him fulfill the terms of the deal. There could also be some other magical creatures or beings that are associated with Death, such as the Grim Reaper - like figures in the wizarding world. And perhaps some powerful wizards or witches who have had past experiences with Death could also be part of the story.