Well, a plot twist might be that Draco, who is supposed to be Voldemort's pet, actually starts to have a strange influence on Voldemort. Maybe Draco's ideas or his unique perspective begin to make Voldemort question some of his own actions or beliefs. Or perhaps there is a revelation that Draco was put in this 'pet' position by someone else as part of a bigger plan, and Voldemort was unknowingly a part of it.
One possible plot twist could be that Draco discovers a hidden power within himself that gives him the courage to stand up to Voldemort. Maybe it's an ancient magic that his family has long forgotten about. This newfound power could make him a real threat to Voldemort's plans.
A third plot twist could involve a character we least expect coming to Harry's rescue. Perhaps a Slytherin student who has been secretly against Voldemort all along. This student could have some inside knowledge about Voldemort's lair and manages to free Harry, leading to a change in the dynamic between the houses at Hogwarts.
Perhaps voldemort's daughter has some hidden power that Draco discovers. This power could be the key to defeating the remaining dark forces in the wizarding world. However, using this power comes with a great risk, and they have to decide if they are willing to take that chance. It would create a lot of tension and moral dilemmas for both characters.
Well, it could start with Draco being forced into this 'pet' - like situation by Voldemort. Maybe at first Draco is terrified, but as time goes on, he might start to understand Voldemort's motives a bit more, and their relationship could become more complex, with Draco having to do Voldemort's bidding while also trying to find a way out.
A really interesting plot twist might be that Voldemort is being controlled by an even darker force, and Harry has to figure out a way to break that control while being held captive. Or perhaps Harry's friends, thinking he is dead, accidentally start a chain of events that end up helping Harry escape in a very unexpected way. For example, Hermione might cast a spell that was supposed to be for protection but ends up creating a portal right in Voldemort's lair.
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.
Perhaps the twist is that Sirius saves Draco, but in doing so, he sacrifices his own freedom. And then Draco has to figure out a way to return the favor and free Sirius. Or it could be that the reason Sirius saves Draco is not what it seems at first. Instead of pure altruism, he has a hidden motive related to his own past or a prophecy that involves Draco.
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 a major plot twist could be that Voldemort actually has a change of heart after 'adapting' Harry. He sees something in Harry that makes him question his own evil ways. This could lead to a strange alliance between the two where they try to find a new way to rule the wizarding world that is less about destruction and more about a new form of magic governance. It would be a very unexpected turn considering Voldemort's character in the original series.
One possible plot could be a moment of unexpected vulnerability for Voldemort. Maybe Draco, in a moment of courage or desperation, hugs Voldemort to show him a different side of humanity, which then makes Voldemort question his own actions.