Slytherin Greatness is a feature in which I explain why non-Harry Potter characters belong in Slytherin. These characters can come from books, movies, or television.
Character
Fang “Rin” Runin

Source
The Poppy War by R.F. Kuang
Why Rin is a Slytherin
In war, there are all kinds of heroes, antiheroes, and villains. Of course, history is written by the victors. But fiction? Fiction is written solely by someone with a story to tell. War stories have followed Gryffindors, Hufflepuffs, Ravenclaws, and Slytherins and the story changes based on which House said protagonist is from. If you ask me, Slytherin soldiers are by far the most interesting.
Enter Fang “Rin” Runin. If she wasn’t as Slytherin as she is, The Poppy War wouldn’t be nearly as good as it is. It’s her ambition and cunning, her ability to sacrifice others for the greater good that makes her so fascinating and so formidable.
Rin starts the story studying for the Keju, a difficult test that determines whether or not you can attend a military academy. She doesn’t do this out of any desire for glory or out of a sense of justice. Rin aspires to be a soldier so she isn’t forced to be an older man’s wife. It’s her way out of her province, her only chance to become somebody.
Moreover, when she’s kicked out of her fighting class, she continues studying on her own time to make sure she keeps up with her classmates. No, not just keep up— surpass. And she succeeds, eventually beating the student at the top of that class.
In her strategy class, she proposes flooding a village as a means of keeping supplies and access away from enemy country Mugen. Though this would lead to civilian deaths, it would ultimately help win the war.
Rin later puts this into practice when she and the Phoenix burn down the entire country of Mugen, thus ending the Third Poppy War. Countless civilians die, but Nikara is able to win the war. Few would make the choice Rin does, but a Slytherin would.
Which leads me to my next point: Rin’s quest for vengeance. Whether against Mugen or against her own empress, Rin’s sense of justice is tied directly to her need for vengeance. Rin allies herself with the Dragon Lord and dooms her country to civil war, but her ultimate goal of revenge outweighs that cost.
However, Rin has little to no desire to be a leader. She’d much rather follow someone like the Dragon Lord so she has someone to blame if things go wrong. This is such a Slytherin move, finding someone you can serve so you can shift any blame for failure onto them.
And what is a Slytherin Greatness post without mentioning that selective loyalty Slytherins are famous for? Rin’s loyalty is absolutely conditional. You have to prove yourself before she trusts you. She’s also really petty about it. If you screw her over, she’ll screw you over. Just ask literally everyone.
Rin also has another lesser known Slytherin trait— it’s her way or the highway. This, I think, is related to the traditionalism of this House. If you don’t see things from her point of view, you are wrong and a host of other relevant negative traits. Since Nezha doesn’t want to be a shaman, he must be a coward. Only Rin’s relationship with shamanism is correct in her mind.
Rin is such a flawed character, but that in and of itself isn’t what makes her a Slytherin. It’s her ambition, her shrewdness, her belief that the ends justify the means. It’s what makes her such a deliciously dark protagonist to follow. And, with her mastery of her shaman abilities, I just know she’s going to end the series a terrifying force to be reckoned with.
What character would you like me to do a Slytherin profile on next? Leave me some suggestions in the comments!