Using the Hogwarts Houses as a basis for character analysis is pretty much my favorite hobby. I guess I’m just weird like that. And while I spend a lot of time thinking about what Houses characters from other stories might be in, I also have a lot of thoughts about the Harry Potter characters themselves, especially those that break House stereotypes. I’ve written about why Luna Lovegood belongs in Ravenclaw and how Peter Pettigrew – one of the most cowardly characters – ended up a Gryffindor. I’ve talked about the ways in which Dumbledore shows traits of all four houses, and I’ve got a growing list in my head of characters I think were probably given the same Gryffindor or Slytherin choice as Harry: Albus Severus Potter, Barty Crouch Sr., Rufus Scrimgeour, and Regulus Black.
Unlike his brother, Sirius, Regulus Black was not a rebel – at least, not at first. He was a Slytherin, like his parents and his cousins, and he later went on to become a Death Eater. He is characterized only through secondhand information from those who knew him and never appears in the story or the flashbacks, but based on Sirius and Kreacher’s descriptions, we can get some idea of his personality.
Dumbledore describes Voldemort’s school friends, and by extension the Death Eaters, as “the weak seeking protection, the ambitious seeking some shared glory, and the thuggish gravitating towards a leader who could show them more refined forms of cruelty” – and that’s a pattern that proves fairly true. Regulus, who was certainly courageous and is never described as being particularly cruel, almost certainly joined out of ambition. He seems to have been eager for his parents’ approval and eager to do great things, but without much discernment or ability to think for himself about who to follow. Ambition is a Slytherin trait, and Voldemort was an expert at tapping into Slytherins’ personal ambitions in order to win their support.
Along with ambition, Slytherins are also supposed to be cunning, which is something Regulus definitely demonstrates. Nobody really knew until decades after his death how he had died or why – not even Voldemort or his own family. He came up with his plan in secret and made sure that it stayed that way, revealing himself only in a hidden note that was set up to not be found until after Voldemort discovered what he had done. That sort of careful planning fits well in Slytherin house. Then again, he planned carefully and executed flawlessly a plan that he knew would result in his own death, and he went through with it because he believed it was the right thing to do. Is that really a Slytherin move, or is it more Gryffindor?
Slytherins are supposed to be “brave … but not foolish” and have strong self-preservation instincts. They put themselves and their own safety first, along with sometimes that of their loved ones. It is Gryffindors who are known for showing selfless courage. They are willing to put themselves at risk, stand up for what they believe in, and lay down their own lives for their cause. A Slytherin who had second thoughts about working for Voldemort might have tried to disappear, changed sides, become a spy, or simply ignored their conscience, but few would have thrown their own lives away in the hopes of making it easier for someone else to defeat him. That’s Gryffindor courage, even if it’s Slytherin ambition that got him there in the first place. The star Regulus is named for is even located in the constellation Leo, and is nicknamed “the lion’s heart” – surely not a coincidence!
But Regulus was not a Gryffindor. Why not? Because Sirius was. Not only did the two brothers not get along, but Sirius was the elder, and his parents did not take it well when he was sorted into Gryffindor. Having seen how furious they were could easily have increased Regulus’ determination to be the “good” son and restore the family honor, leading him to choose Slytherin in much the same way that Harry chose Gryffindor. You could even say that Regulus Black is one of Harry’s foils, a Dark Side character with a huge self-sacrificial streak and a ton of Gryffindor bravery to contrast with Harry’s own secret: that he was almost put in Slytherin house.