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.
One plot idea could be that Harry struggles with his new identity. He might be shunned by some in the wizarding world who fear his connection to Voldemort, while others might try to use him for their own gains. Another could be that he discovers hidden powers within himself that are related to Voldemort's lineage, and he has to learn to control them without succumbing to the dark side.
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 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.
Perhaps in this fanfiction, Harry discovers some dark secret about the Order of the Phoenix or Dumbledore that makes him lose faith in the side he has always been on. This, combined with Voldemort's manipulation, could lead him to side with the Dark Lord. For example, if he finds out that Dumbledore has been using him all along without his full knowledge, he might be so disillusioned that he turns to Voldemort as an alternative.
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.
Well, it could be that in this fanfiction, Harry discovers some long - hidden truth about the wizarding world that makes him realize Voldemort's motives aren't entirely baseless. Maybe there's a prophecy misinterpretation that leads Harry to think they can work together to fix the wizarding world's problems.
One important plot point is the change in Harry's relationships. For example, his friendship with Ron and Hermione would be severely strained. Hermione might try to find a way to save Harry from Voldemort's clutches through research, while Ron could be more hot - headed and feel betrayed. Also, Voldemort might use Harry to gain access to certain secrets or artifacts that he couldn't reach before. Maybe the Philosopher's Stone again, or some other powerful magical item hidden in Hogwarts. This would create a whole new set of challenges for the characters in the fanfiction.
Yes, the world of fanfiction is vast and full of strange and wonderful ideas. There might be some fanfiction out there where Harry Potter is Voldemort's grandson. Fanfiction writers often like to play with the established relationships in the original work and come up with really unique concepts. They might rewrite the story from this new perspective, changing many of the events and character interactions in the process. But to actually find such a fanfiction, one would probably need to search through various fanfiction websites.
Well, one way could be through some dark and misinterpreted magic. Maybe Harry stumbles upon an ancient spell that he thinks will defeat Voldemort once and for all but instead, it backfires and revives him. It could also be due to some sort of interference from a powerful dark object that Harry unknowingly uses in the wrong way.
Themes could include the blurred lines between good and evil. If Harry is a fan of Voldemort, it challenges the traditional view of their roles. Another theme might be the exploration of dark magic. Since Voldemort is associated with it, Harry's fascination could lead to a deeper look into the nature of dark magic.