One possibility could be that Arcturus Black imparts unique magical skills to Harry Potter. Maybe he teaches Harry some ancient and powerful spells that are not commonly known at Hogwarts. This could give Harry an edge in his battles against Voldemort and his Death Eaters.
In this fanfiction, Arcturus Black might train Harry Potter in stealth and secrecy. Given the dangerous times they live in, Arcturus could see the need for Harry to be able to move about undetected. He could teach Harry how to use magic to cloak his presence, not just from Death Eaters but also from other potential threats within the wizarding world. This training could be crucial for Harry when he embarks on dangerous missions, like infiltrating Voldemort's lairs or uncovering the secrets of the Dark Arts that Voldemort is using.
In the fanfiction, Arcturus Black is likely an important figure in the wizarding world. He might be a powerful and knowledgeable wizard from the Black family. Maybe he has a long - standing reputation for his magical abilities and wisdom, which is why he is chosen to train Harry Potter.
One possible plot could be that Harry discovers a long - hidden connection between his family and Arcturus Black. Maybe Arcturus has some secret knowledge about Harry's parents or his destiny. They could team up to fight against a new dark force emerging in the wizarding world, with Arcturus using his old - fashioned but powerful magic and Harry his more modern skills learned at Hogwarts.
Well, one possibility could be that Arcturus Black uses his powerful magic skills to rescue Harry from a dangerous situation. Maybe Harry is trapped in a dark wizard's lair, and Arcturus arrives just in time to fend off the bad guys with his advanced spells.
Arcturus Black might be portrayed as a wizard with a deep understanding of ancient magic in the fanfiction. He saves Harry Potter perhaps because he sees in Harry the potential to defeat the dark forces that are plaguing the wizarding world. His character could be a blend of mystery, power, and a sense of moral obligation towards Harry.
A major theme is the uncovering of secrets. In many of these fanfictions, Arcturus Black holds some sort of secret knowledge related to the wizarding world, perhaps something about the Dark Arts or the history of Hogwarts. Harry, being the curious and brave character he is, is drawn into this web of secrets. And also, friendship is a theme. Despite the age and family differences, a bond of friendship or a deeper connection forms between them.
Maybe it's a group of dark wizards who believe in a more extreme form of pure - blood ideology. They see Arcturus Black as a traitor for teaming up with Harry Potter, who is a half - blood. They plot to take over the wizarding world and eliminate anyone who doesn't fit their idea of a pure - blood wizard.
One possibility is that Harry discovers a world where fanfiction has the power to change the real wizarding world. So he has to train to fight against the alterations caused by these fictional stories. For example, if a fanfiction made Hogwarts a place full of dangerous magical beasts that don't belong there, Harry would need to train to restore order.
Well, perhaps Harry could be trained in some long - lost or dark magic that Dumbledore has been hiding from him. This new training might make him even more powerful than before, able to defeat Voldemort in a more spectacular way.
Maybe Harry discovers some long - lost magic techniques taught by Godric. He could become super powerful and use ancient spells to fight Voldemort.
Well, in this fanfiction, it could be that Hephaestus trains Harry Potter to have a better understanding of the more physical and mechanical aspects of magic. For example, he might learn to build magical devices that can be used in battles or for other important tasks. This would give Harry an edge over his enemies as he'd have skills that no other wizard has. It could also lead to new alliances as other wizards might be interested in his newfound abilities.