The imagery of a possessed Professor Quirrell prowling the Forbidden Forest and drinking unicorn blood to sustain Voldemort is straight up nightmare fuel. The series got darker as it progressed, but that incident being in the first book is still one of the freakiest things.

The movies did a great job in capturing that scene too.

It portrays Quirrell/Voldemort as something inhuman and otherworldly. Feels like Harry just walked into a Nazgul. IMO it was the scariest Voldemort felt in the series even though we never even see him. It was something straight out of a horror film.

I think the freakiest part is how the film made him seem almost "floaty", like as if he was levitating. Like when Firenze drove him away, it briskly slipped into the fog. I don't know why but that imagery of a possessed human controlled by Voldemort floating in the forest, feasting on unicorns is just so messed up is absolutely chilling and I'm shocked its in the very first book.

One of the creepiest bits about Voldemort are the descriptions of his time when he lost his body and hid out in Albania. We aren't told much, but everything we do know makes him sound like a true monster, barely even human. It's like we saw a glimpse of what Voldemort's life was as a symbiotic parasite that could only live in a hosts body.

It's honestly peak horror in Book 1 of a series that's supposedly about a kid going to a fun magic school.