Maybe some new characters from the demigod side could also be main characters. For example, a demigod like Percy Jackson could be introduced to the Hogwarts world. And of course, Dumbledore would also play an important role as he guides the students in Hogwarts and would be involved in any new discovery like learning about demigods.
Well, it could be about the students at Hogwarts in the Harry Potter universe learning about demigods. Maybe they discover the existence of demigods from Greek or Roman mythology and how their powers and worldviews differ from wizards and witches. It might involve some sort of cultural exchange within the fictional realm, like sharing magic and skills.
Since it's a fanfic, the main characters could be the ones doing the asking. It might be a young protagonist, like a curious teenager who has just discovered the existence of demigods and wants to know all about them.
There could be his arithmancy teacher as a main character too. This teacher might be strict but also very knowledgeable, guiding Harry through the difficult subject.
In the 'Harry Learns Alchemy' fanfic, Harry is the central figure. He is on a journey of learning alchemy. Hermione would be a key character as she is very studious and would be eager to help Harry understand the complex concepts of alchemy. There could be a mysterious old wizard who acts as a mentor to Harry in his alchemical studies. And Ron, as Harry's best friend, would be around, maybe not fully understanding alchemy but being supportive in his own way.
Obviously, Harry Potter is one of the main characters as it's about him learning magic. He is the central figure around which the story revolves.
Since it's about Harry learning the old ways, Harry Potter is surely one of the main characters. There might also be some old - time wizards or witches who teach him the old ways.
Obviously, Harry would be one of the main characters as it's about him learning lost arts.
Obviously, Harry would be one of the main characters. Since it's about him learning family magic.
I'm not familiar with this fanfic enough to name the main characters. It could be well - known female characters from the Hogwarts world like Hermione, Ginny, or Luna.
Since the title mentions Barry, he's definitely one of the main characters. There might be others like his friends or mentors who help him in learning the infinite mass punch, but without reading the fanfic, it's hard to say exactly who else would be a main character.