In this fanfiction, Lucius might deage Snape as a form of punishment. Snape, being 16 again, has to navigate Hogwarts all over again. He might be more vulnerable in this state, and the story could explore his relationships. He could re - experience his old rivalries, like with James Potter, but this time with the knowledge he has from his adult life. Also, there could be a sub - plot about him trying to reverse the deaging spell while also dealing with the chaos that his new, younger self is causing in the wizarding world.
It could be that Lucius accidentally deages Snape while trying out a new, experimental spell. Then, the story could revolve around how Snape has to deal with being 16 again in a world that has moved on. He might struggle with his memories of the future and how to interact with people who knew him as an adult. For example, he'd have to face his former students who are now his peers, and that could create some really interesting and complex situations in the fanfiction.
Maybe Lucius deages Snape out of jealousy. Snape was always a bit of a rival in Voldemort's eyes. In his deaged state, Snape might form unexpected friendships with students at Hogwarts. He could befriend Hermione, for example, who would be intrigued by this strange new version of Snape. Meanwhile, Lucius has to keep his actions a secret from Voldemort, as Voldemort might not be happy with his meddling in Snape's life.
One possible plot could be Snape having to re - experience his Hogwarts years at 16. He might struggle with his old memories while also dealing with the current Hogwarts environment. For example, he could have a different perspective on his relationships with other characters like Lily. Maybe he tries to change things that he regretted in his original past.
Snape's deaged personality could also be more impulsive. Without the restraint of his adult self, he might act on his emotions more quickly. For example, if he felt wronged, he might lash out immediately instead of plotting a long - term revenge like his older self would do. Also, he could be more curious about the world around him, eager to explore magic in a new way that his older self had forgotten due to years of being jaded.
I'm not sure of a specific fanfiction with this exact plot, but you could try searching on popular fanfiction platforms like Archive of Our Own. Use the tags 'Snape', 'deaged', 'Lucius' and '16' to narrow down your search.
In deaged Snape fanfiction, the theme of redemption can be quite prominent. It gives Snape a chance to rewrite some of his past actions or at least be seen in a new light. There's also the theme of identity crisis. He's not the same old Snape, and he has to figure out where he fits now. Additionally, the theme of adaptation is common. He has to adapt to his new physical state, new social situations, and new magical abilities or limitations that come with being deaged.
In a fanfiction with this premise, perhaps Lucius discovers a way to control Harry using some ancient and dark magic. Harry is then made to serve Lucius in his Malfoy Manor. The plot could involve Harry learning about Lucius' secrets and using that knowledge against him. There could be a sub - plot about Harry's friends trying to rescue him. As Harry endures the hardships of being a slave, he also discovers new aspects of his magic that he can use to fight back. This would be a very dark and angsty plot compared to the original Harry Potter stories.
You can start by looking on fanfiction platforms like FanFiction.net or Archive of Our Own (AO3). These sites have a vast collection of fanfiction, and you can simply search for 'deaged Severus Snape' in their search bars. There are often tags and filters on these sites that can help you narrow down your search further, such as by rating, length of the story, or the specific era in the Harry Potter universe that the story is set in.
Snape could also be acting out of a sense of justice. Lucius was a Death Eater, and Snape, despite his own past as a Death Eater, had turned against Voldemort. Saving an innocent, especially Harry's daughter, from Lucius would be in line with his new allegiance to the side of good.
Snape and Lucius can be presented in various ways in fanfiction. One common portrayal is that Lucius, being from a wealthy and influential pure - blood family, may look down on Snape at first due to Snape's half - blood status. But as they grow older, they find common ground in their service to Voldemort (although Snape has his own hidden motives). Their relationship might be full of intrigue and hidden agendas.
In the fanfiction world, if Snape was deaged to 16 by a potion, he might have a whole new set of challenges. Firstly, his relationships would change. He'd probably have a different dynamic with his peers at Hogwarts. His knowledge and skills would still be there, but his physical and emotional state would be that of a 16 - year - old. He might struggle to be taken seriously by those who knew him as an adult, and his interactions with students could become more complex as he'd be closer in age to them.