There could be a new character, a mysterious old wizard who has some past connection with Nagini. He could be a mentor figure to Albus, guiding him in understanding the nature of the servant. This old wizard might have some secrets about Nagini and her servant that could be the key to resolving the conflict in the fanfiction.
Rose Granger - Weasley could also be a main character. Given her intelligence and her family's history, she could play a crucial role. She might be the one who discovers some important clues about the servant of Nagini through her research in the Hogwarts library. And she could use her magical skills, which she has inherited from her parents, to assist Albus and others in dealing with the servant.
In this fanfiction, it might be that the servant of Nagini has a change of heart. Albus Potter could be the catalyst for this change. He could show the servant the error of their ways, and they could then join forces to fight against the dark forces that still linger in the wizarding world. This could involve battles with dark wizards, solving magical mysteries, and ultimately, a journey of redemption for the servant of Nagini.
Maybe Albus has done something dangerous or disobeyed Harry's instructions. For example, if Albus got involved with some dark magic related stuff without Harry's knowledge, that would surely make Harry yell at him.
It could be a descendant of one of the Death Eaters who holds a grudge against the Potter family. They might try to finish what Voldemort started and target Albus specifically.
Harry Potter himself could be the Servant of God. Given his central role in the original series, it would make sense for him to take on this new identity in the fanfiction. He has always been a figure of good, and this could be an extension of his character arc, where he now serves a higher power in a more direct way.
Obviously, Albus Potter and the Marauders - James Potter, Sirius Black, Remus Lupin and Peter Pettigrew. There might also be some other characters like Albus's friends or professors who could be involved in the story.
The main characters are obviously James Albus and Lily Potter. They are likely to be the central focus of the fanfiction, with their adventures and experiences at Hogwarts being the main storyline.
Luna Lovegood's daughter could be a potential girlfriend. Given Luna's unique and open - minded nature, her daughter might inherit those traits. She could be someone who is interested in the same mysterious and off - beaten - path aspects of the wizarding world as Albus, and they could bond over that. Their relationship might also be a connection between two different generations of Hogwarts students.
There could be a new dark force in the wizarding world that kidnaps Albus as a way to gain power. They believe that Albus has some sort of latent magic or knowledge that can be harnessed for their evil purposes. Maybe they have some prophetic vision that led them to target Albus specifically.
Most likely, his parents, Harry and Ginny Potter, could send the howler. They would be concerned about their son's well - being and actions at Hogwarts. If Albus got into trouble or was not living up to the Potter family name, they would not hesitate to send a howler to set him straight.
His family members also play roles. His father, Harry Potter, could be mentioned, perhaps giving Albus advice or being a source of inspiration. His siblings might also be included, adding family - related sub - plots to the story.