Dressed as a Hogwarts portrait

Others dress up as characters to participate in the plot, but he wears as the background... Is there a more miserable life in HP than him?Perhaps, now is not the time to worry about this matter, he should crash "How to Make a Qualified Portrait - Hogwarts Edition", so that he will not be treated as a dangerous item by the administrator Filch or others .But the more critical issue is that the portraits in the wizarding world are all alive. He doesn’t know the name of this portrait. Who has long black hair and green eyes—who hung a mirror opposite his painting, it’s so necessary. I am so grateful——on the ancient but still brightly colored canvas, a boy in tight black tights and a gorgeous cloak is smiling at himself in the mirror. There are three curved ancient Greek letters above the frame, and Below are also eight more curved Greek letters~~ Only in the far right corner of the canvas, there are two slanted and gorgeous English letters: SS Well, I glanced at the cuffs decorated with lace, at least now the only thing that can be sure The most important thing is that he is definitely not the potions professor, and that professor will never tolerate the existence of a portrait of himself in such clothes.So, who is he?Content tags: HP Magic Moment Rebirth┃ Search keywords: Protagonist: Salazar Slytherin┃ Supporting roles: Severus Snape, HP and others