The vampire could be a new teacher at Hogwarts. Snape would be very suspicious of this new arrival. Draco might be curious or even a bit scared, but tries to hide it. Harry would be on high alert. The vampire could then start to show some strange behavior, like being interested in certain students' blood, which would set off the whole plot.
Perhaps the vampire is a lost soul seeking redemption. It approaches Snape first, thinking he can help due to his complex past. Draco, who is always looking for a way to prove himself, sees this as an opportunity to show his bravery or gain some power. Harry, on the other hand, is skeptical but realizes that the vampire might be the key to solving some other mystery in the wizarding world. Their interactions with the vampire would be shaped by their own characters and goals.
One idea could be that a vampire infiltrates Hogwarts and Snape, Draco, and Harry have to put aside their differences to deal with it. Maybe the vampire has a special connection to the dark arts, which Snape is intrigued by while Draco is initially tempted by the vampire's power, and Harry is just determined to protect the school.
Well, he could be integrated as a powerful witch. In the lore of Arthur Pendragon, there are often elements of magic associated with him. In The Vampire Diaries, witches play a significant role. So, Arthur could be a very old and powerful witch whose magic has a different flavor compared to the local witches. His presence would disrupt the power balance among the witches in Mystic Falls and attract the attention of vampires and other supernaturals.
Well, if Snape turns Harry into a vampire in fanfiction, it would completely change the dynamic. Harry would have to deal with new instincts like the thirst for blood. His relationships would be strained as his friends might be scared of him. Also, his role as the 'Chosen One' would be redefined as he's now a different kind of being with different needs and abilities. He might have to struggle between his human side and his new vampire nature.
Well, perhaps Snape sets them to clean the potions classroom. Draco tries to boss Harry around at first, but Harry refuses to be pushed. As they clean, they accidentally knock over a vial that releases a magical mist. The mist makes them relive some of their worst memories involving each other. This forces them to understand each other's perspectives better and by the end of detention, there's a less hostile air between them.
Well, it could be that in the 'Harry and Draco apprentice with Snape' fanfiction, they end up learning a lot about the Dark Arts from Snape, not in an evil way but in a way to defend against them. Harry would be skeptical at first but then realize the importance. Draco might be more eager as he has some knowledge of the Dark Arts from his family. Snape could also teach them how to brew complex potions that are useful in both dueling and healing. There could be some rivalry between Harry and Draco in terms of who can master the skills faster, but also moments of cooperation when they face difficult tasks.
Well, Snape might use his knowledge of both boys' strengths and weaknesses. For Harry, he'd understand his Gryffindor courage but also his impulsive nature. With Draco, he'd be aware of his Slytherin pride and family influence. Snape could set similar rules for them in terms of magic study and behavior, while also respecting their individual personalities. He might encourage Harry to be more cautious and Draco to be more empathetic.
Snape might also keep what he saw to himself at first. Instead of immediately confronting them, he could choose to observe them further. He might be curious about what they were really up to and use his skills as a spy to find out more. This way, he could gather more information before deciding on the best course of action, whether it be punishment or something else entirely.
Perhaps Snape would force them to work together on a task as punishment. This could be something like cleaning the Potions classroom without magic or helping in the Forbidden Forest. During this time, they might start to understand each other better. Harry could see that Draco isn't just a spoiled brat all the time, and Draco could see that Harry has more depth than he initially thought.
If Snape adopts Harry and Draco, it could change the whole dynamic of Hogwarts. Snape would have to ensure that both boys are getting proper magical education while also taking care of their emotional well - being. Harry might start to see Snape as more than just a teacher who was always tough on him. Draco would be forced to interact with Harry in a more positive way. There could be some really heartwarming moments as Snape tries to show his affection for the two boys in his own, rather gruff way. And perhaps they could all form a strong, if unconventional, family unit.
Perhaps Snape gives them the talk about the importance of unity in the face of the dark forces that are always lurking. He could be using his own experiences to make them understand that they should put aside their differences for the greater good. For example, he might talk about how during the war, internal disputes among wizards only made it easier for Voldemort to gain power. By uniting, they could be a stronger force against any potential threats. Also, Snape might use this talk to make them realize that their personal grudges are petty compared to the bigger issues at hand.