One possible plot could be that Snape, despite his initial resentment towards James Potter (Harry's father), sees the vulnerability in little Harry. He decides to take him in out of a sense of duty to Lily (Harry's mother). Snape then has to adjust his life to care for a child. He teaches Harry potions at an early age and tries to protect him from the darker elements in the wizarding world. Harry grows up with a different perspective on Snape than in the original story.
Snape would likely become more nurturing. Instead of just being the strict and often cold Potions master, he would have to show a softer side to take care of Harry. He might be more patient as he guides Harry through his magical education and daily life.
It could be an orphaned wizard child from a family that was killed by Death Eaters. This would give Snape an added sense of responsibility as he might feel guilty for being associated with the Death Eaters in the past.
Snape's character often develops from a cold and aloof figure to a more caring and nurturing one. At first, he might be hesitant and gruff, but as he spends more time with Harry, his protective instincts kick in. He starts to show more patience and understanding, which is a big change from his usual self in the original series.
In such a fanfiction, one possibility is that Snape would initially struggle with his new role as an adoptive father. He has a complex personality, but over time he might start to show his protective side towards Harry and Hermione. He could teach them advanced magic, especially his own areas of expertise like Potions, in a more personalized way.
In some 'Snape Adopts Harry' fanfictions, there is a plotline where Snape and Harry have to work together to uncover a mystery at Hogwarts. This mystery could be related to the Dark Arts or some hidden secrets of the school. Along the way, their relationship evolves from a reluctant guardian - ward relationship to a more loving father - son bond. Harry might start to understand Snape's past actions and Snape, in turn, learns to open up and be more affectionate towards Harry.
In this kind of fanfiction, perhaps Severus Snape and Tom (presumably Voldemort in his Tom Riddle form) would have a very different dynamic with Harry. Maybe they would try to shape Harry's magical abilities in their own ways. Snape might use his knowledge of potions and dark magic to train Harry, while Tom could introduce Harry to some of the more complex and dangerous aspects of magic from a different perspective.
Well, it could be a really interesting story. Snape, being the one to adopt Harry, would have to deal with his own complex feelings towards James Potter while raising Harry. He might initially be strict, but gradually, as he sees Harry's own personality develop, he'd grow to have a very deep and loving bond with him. He could also introduce Harry to a different side of the wizarding world, one that is more influenced by his own Slytherin roots.
Snape's character often develops from a cold and aloof figure to a more caring and father - like one. He starts to see Harry not just as James Potter's son but as an individual he is responsible for. His protective instincts grow, and he becomes more patient. For example, he might initially snap at Harry for small mistakes but over time, he learns to guide him gently.
Snape's character development in this fanfiction would be quite complex. At first, he might be very hesitant and unsure of how to be a father. But as he spends time with Harry, he'd gradually let down his guard. He'd find himself enjoying the simple joys of seeing Harry learn and grow. His relationship with the other Hogwarts staff might also change. He could become more collaborative as he realizes he needs support in raising Harry. His loyalty would still be there, but it would expand to include his newfound family with Harry. This would completely transform his character from the bitter and vengeful man he was in the original story into a more well - rounded and loving person.