Well, his motive might be related to his twisted sense of love. In the context of fanfiction, Hannibal could think that by kidnapping Will, he is protecting him. He may view the world as a dangerous place for Will, and his actions are a way to keep Will safe in his own, very abnormal way. Also, it could be a power play. He wants to show that he has the power to take Will whenever he wants, asserting his dominance over Will.
Perhaps it's a power play. Hannibal is a character who enjoys being in control. By kidnapping Clarice, he asserts his dominance over her. He can manipulate the situation, make her dependent on him in a way, and show that he has the upper hand. It's like a game to him, and Clarice is the most interesting piece on the board.
One possible motive could be his obsession with Will. Hannibal sees Will as a unique individual, almost like a kindred spirit in some ways. He might kidnap Will to have him all to himself, away from the outside world that he believes corrupts or misunderstands Will.
At first, Will would be in shock. But as time passes, he would start to analyze Hannibal's motives. He is a profiler, after all. He might try to use his psychological knowledge to manipulate Hannibal in return. He could also go through periods of anger, resenting Hannibal for taking away his freedom. And there might be moments of confusion as he tries to figure out if there is any part of Hannibal's actions that could be considered 'caring' in his warped way.
Clarice could also become very defiant. She is a strong - willed character. So, instead of cowering, she might constantly challenge Hannibal, trying to get under his skin and make him make mistakes. This could lead to some intense mental battles between them within the fanfiction.
Well, one possible motive could be power. Maybe he thinks by kidnapping Tea, he can gain some sort of leverage over Yugi or the others. In the Yu - Gi - Oh world, power is often a driving force. Another reason might be revenge. If he has some past grudges against Yugi or his friends, using Tea as a pawn could be his way of getting back at them.
One possible motive could be power. Maybe Marik believes that by sacrificing Anzu, he can gain some dark and powerful magic in the Yu - Gi - Oh universe. Another reason might be revenge. If he has some grudge against the main characters associated with Anzu, he could be using her as a pawn to get back at them.
Yes, there are some fanfics where Will is depicted as Hannibal's son.
Will might initially be in shock. He trusts Hannibal to a certain extent, so the betrayal of being kidnapped would be a huge blow. He could be angry and try to fight back against Hannibal.
There's this one called 'The Dark Alliance' that's really good. It has a great plot and character development.
One possible motive could be Severus' complex relationship with Harry's father, James. Maybe Severus feels a deep - seated resentment towards James and by kidnapping Harry, he wants to get some form of revenge on the Potter family. Another motive could be related to the war. He might think that by having Harry in his custody, he can use Harry as a bargaining chip either with Voldemort or the Order of the Phoenix. He could also believe that he can protect Harry better than others, in his own, rather extreme way, thinking that others in the wizarding world are not capable or trustworthy enough to keep Harry safe.