The thing that the history books had always forgotten was that Salazar Slytherin had been the second son. And that it had been his brother, Othello, who had inherited the parseltongue gene. He had a different ability.
He was angry.
He tried hard not to let it overwhelm him but at the end of the day he would always be holding on by a thin thread of nerve.
In truth he was surprised it had not happened earlier. The witch burnings had always forced him close to the edge but this time it was personal.
His own sister –fiancée– sister, because he could never see any member of the Gryffindor clan in a romantic light was being burnt.
At the stake.
Right in front of him.
His anger manifested and grew until the entire village was burning. Until there was nothing but flames and pain and rage. His rage.
Later, when his three friends – four, there should be four – pulled him back, grounded him so that he could reign himself in, he regretted it.
He regretted that the villagers who had not been watching the burning had died. The rest of them he couldn't care less about.
He never told his friends that though. He let them think he was good.