Another great read could be 'The Malfoy - Potter Bond'. Here, Lucius' adoption of Harry is not just about protecting him, but also about forging a new alliance between the Malfoy and Potter families. It's interesting to see how the two characters interact and how the wizarding community reacts to this strange new arrangement.
Often, it starts with Lucius noticing Harry's situation. Maybe he sees Harry being mistreated in Diagon Alley or hears rumors about his life at the Dursleys. Then he decides to take Harry in, which shocks everyone around them. After that, they usually have to deal with the fallout from the wizarding community, who are suspicious of Lucius' motives.
One great fanfiction in this genre is 'A New Beginning' where McGonagall steps in to rescue Harry from his abusive relatives. It beautifully shows how she nurtures him and helps him grow in confidence.
In such a fanfiction scenario, Harry might be exposed to a very different upbringing. Lucius could try to indoctrinate Harry with pure - blood supremacist ideas at first. But as time goes on, Harry's strong sense of justice might conflict with Lucius's beliefs. Maybe Harry would gradually change Lucius's view on Muggle - borns, or he could use his influence within the Malfoy family to bring about some positive changes in the wizarding world's view on blood purity.
Well, the theme of protection is quite prevalent. Sirius is very protective of Harry in these fics. Also, the theme of discovery. Harry discovers a new side of the wizarding world through Sirius. And friendship is also a big part. Harry makes new friends as he starts a new life with Sirius. These themes together create a rich and engaging story.
One possible plot could be that Severus discovers the extent of Harry's abuse at the Dursleys. He decides to take Harry in out of a sense of duty or perhaps a hidden soft spot for the boy. He then has to teach Harry about magic in a more personal and nurturing way, different from Hogwarts. They might also face opposition from the wizarding community who question Severus' motives.
One popular 'sirius adopts abused harry fanfiction' is 'The Debt of Time'. It delves deep into how Sirius takes Harry under his wing after realizing the extent of his abuse at the Dursleys. The story beautifully portrays their growing bond and how Sirius helps Harry heal from his traumas.
He would become more nurturing. Usually, Severus is seen as cold and aloof, but with Harry in his care, he'd have to show more warmth. He might still be strict, but it would be out of love for Harry's well - being rather than just being his usual harsh self.
His life would change drastically. He'd be living in a different environment, with different values being pushed on him. Instead of the Dursleys' neglect, he'd face Lucius's attempts to mold him into a pure - blood - ideal wizard.
Well, it's the contrast. In the original, Harry endures so much at the Dursleys. But in these fanfictions, he gets to experience a real family environment with McGonagall. Also, it allows for exploring new relationships within the Hogwarts community as Harry is now under McGonagall's wing. He can interact with his classmates and teachers in a new light, which makes for really interesting storylines.