As anyone who's ever dipped a toe into the Harry Potter universe can tell you, potions—taught primarily by Professor Snape throughout the books—is one of the most challenging (and rewarding) parts of the Hogwarts curriculum. And it works that way because it's mirrored after chemistry, J.K. Rowling's own least favorite subject in school.

In yesterday's addition to 12 Days of Pottermore, Rowling says she wanted Snape, as one of Harry Potter's most relentless antagonists at Hogwarts, to also teach the most stressful and agonizing school subject:

Chemistry was my least favourite subject at school, and I gave it up as soon as I could. Naturally when I was trying to decide which subject Harry's arch-enemy, Severus Snape, should teach, it had to be the wizarding equivalent. This makes it all the stranger that I found Snape's introduction to his subject quite compelling ('I can teach you to bottle fame, brew glory, even stopper death…'), apparently part of me found Potions quite as interesting as Snape did; and indeed I enjoyed creating potions in the books, and researching ingredients for them.

QUICK. Name what your best Hogwarts subject would be! Mine's probably Divination because I'm bleak and dramatic and good at bullshitting.

Image via Warner Bros.