There's also 'Draco's Salvation of Harry'. It delves deep into the reasons why Harry was being abused and how Draco, who has his own growth arc in the story, manages to rescue Harry. It shows the transformation of their relationship from rivals to something more like protectors of each other.
One common trope is the 'unlikely hero' where Draco, who was once seen as an antagonist, becomes Harry's savior. Another is the 'healing journey' for Harry as he recovers from the abuse with Draco's help. There's also often the 'forbidden friendship' trope as they come from different sides of the wizarding world.
There's a fanfic titled 'Snape's Redemption in Harry's Abuse'. This story focuses on how Snape, who has his own complex past with Harry's father, realizes that Harry is a victim of constant abuse. He decides to use his position as a teacher and his skills in potions and magic to keep Harry safe. It delves deep into the relationship between Snape and Harry, exploring themes of forgiveness and second chances.
Fanfiction.net could also be a place to search. However, the tagging system there might not be as refined as AO3. But if you patiently browse through the Harry Potter section and keep an eye out for the key elements of Blaise and Draco saving an abused Harry in the summaries or titles, you may come across some relevant stories.
You might want to check out 'Secrets Unveiled'. In this story, Draco discovers Harry's abuse by accident when he follows him to an abandoned part of the school.
Harry's reaction would be complex. He has been at odds with Draco for so long that this revelation completely changes the dynamic. He would likely experience a sense of disbelief that such a thing could be happening to Draco. As he processes it, he would start to feel empathy towards Draco. Harry might approach Draco cautiously at first, not sure how Draco would respond to his newfound knowledge. But he would be determined to help in some way, whether it's by using his influence in the wizarding world or just being there for Draco as a friend. This could also lead to a significant shift in the relationship between the Gryffindors and Slytherins as a whole, as Harry's actions towards Draco could inspire others to look at Slytherins in a different way, seeing that they too can be victims of difficult situations.
Draco's reaction could be complex. He has been brought up in a certain environment where showing weakness is not acceptable. But when he discovers Harry is abused, he may find it difficult to ignore. He might start by being a bit standoffish as he processes this new information. However, deep down, he might feel a growing empathy for Harry. His actions could range from small gestures of kindness, like leaving a potion that could help heal Harry's wounds secretly, to gradually becoming more open about his concern and trying to get Harry away from the source of abuse. This discovery could be a turning point in their relationship, leading to a deeper understanding and connection between them.
One plot idea could be that Voldemort saves Harry from his abusers in the Dursley household because he realizes Harry's potential is being squandered there. He then takes Harry under his wing, not to turn him evil, but to train him in magic in a very different way than Hogwarts. Maybe he wants to use Harry as a tool against the Ministry, which he believes is corrupt.
Harry's character would likely become more complex. Initially, he might be distrustful of Voldemort's motives but also feel a sense of obligation for being saved. This could lead to him being more cautious and calculating in his actions, as he has to navigate the dangerous waters of being associated with the Dark Lord.
One common plot is that Blaise and Draco initially notice Harry's abuse in a somewhat accidental way, like during a Hogwarts event or in a shared class. They then decide to keep an eye on him secretly. As they get to know Harry better, they realize the extent of his abuse and start taking more direct actions to protect him, such as standing up to his abusers or finding ways to get him away from dangerous situations.