One interesting plot twist might be that Harry's connection to Odin causes a rift between him and Dumbledore. Dumbledore, fearing the unknown powers that come with Odin's heritage, tries to limit Harry's access to that side of his magic. Meanwhile, Voldemort could be secretly making a deal with a Norse dark entity to counter Harry's newfound strength. And then there's the twist where Harry discovers that his parents' death was somehow related to Odin's enemies in the Norse realm, and he has to avenge them not just against Voldemort but also against these new foes.
In this fanfiction, a great plot twist could be that the magic of the wizarding world and the powers of the Norse gods are actually two parts of a greater, ancient magic. When Harry discovers he's Odin's grandson, he starts to unlock this greater magic. However, this also awakens an ancient evil that was sealed away long ago. This evil targets Harry because of his unique connection. As a result, Harry has to not only deal with Voldemort but also this new, more powerful threat. His friends and the wizarding world have to decide whether to support him or abandon him in the face of this new danger.
A possible plot twist could be that Odin has an ulterior motive for Harry being his grandson. Maybe he wants Harry to bring about a new order in the wizarding world that aligns with the Norse gods' plans. Another twist could be that the Death Eaters somehow find out about Harry's connection to Odin before he does and try to use it against him. They could attempt to steal Odin's power from Harry or use it to manipulate him into joining their side.
One possible plot point could be the discovery of this relationship. Maybe Harry finds some hidden magical artifact or document that reveals the truth. Another could be the reaction of the wizarding world. Would they still see Harry as a hero or would they be suspicious of him? Also, Voldemort's reaction if he were to find out before his death could be interesting. He might try to use Harry for his own ends in a different way than in the original story.
Maybe it implies that the magic in Harry Potter has some connection to Odin's power in Norse mythology. So the spells cast by wizards could be related to the magic Odin wields in his own realm. For example, the Patronus charm could be seen as a form of magic similar to Odin's ability to send out his ravens to gather information.
A plot twist could be that Dumbledore faked his own death to test Harry's loyalty. But when Harry starts to turn on him, Dumbledore realizes his plan backfired. This would create a lot of tension and conflict between them, and also force Harry to re - evaluate his entire relationship with Dumbledore.
One possible plot twist could be that Harry's siren - raised nature makes him a target for dark wizards who want to use his unique abilities for their own gain.
A plot twist could be that Dudley has some latent magical ability that is awakened when he is in a life - or - death situation with Piers. This would completely change their relationship with Harry as now Dudley is also part of the magical world in a way.
One plot twist could be that Harry is actually a double agent. He pretends to be fully under Voldemort's control while secretly working against him. Another could be that Voldemort's training awakens a hidden power in Harry that is neither good nor bad, but something completely unexpected that changes the whole dynamic of the wizarding world.
One possible plot twist could be that Lucius Malfoy has a secret alliance with Dumbledore all along and saves Harry to fulfill some greater plan against Voldemort. Another could be that Narcissa Malfoy, out of a mother's love for all children (not just her own), decides to protect Harry. Or perhaps Draco Malfoy betrays Voldemort's orders to kill or capture Harry because he has developed an unexpected friendship with Harry during their years at Hogwarts.
Another plot twist could be that the magic in the Harry Potter universe is actually a precursor to the Force. Harry Potter discovers that his magic has the potential to evolve into the Force - like powers. This revelation makes him question his place in the wizarding world and whether he should pursue a different path, one that is more in line with what Luke Skywalker represents in the Star Wars universe.
A plot twist might be that when Harry goes to Voldemort, he discovers that Voldemort has a secret weakness. Maybe it's related to his family or some long - forgotten magic. Harry then has to decide whether to use this weakness against Voldemort or try to redeem him. This would add a whole new layer of complexity to the story. Another aspect could be that there are other forces at work, like a third - party wizard who is manipulating both Harry and Voldemort for their own gain, and Harry has to figure out who this is while dealing with Voldemort.
One possible plot twist could be that the daughter of death is initially thought to be on the side of evil but is actually a key to saving the wizarding world. Another could be that she has a secret connection to a major character from the original series that changes everything. Maybe she's related to Dumbledore in some way.