Upd - Thedeepdarkakagueulesnoires2023480pblur

The film you are referencing, (original French title: Gueules Noires

Within 90 seconds, the thread was deleted. Within 3 minutes, his IP was geolocated to a coordinate in the Ardennes forest—specifically, the entrance to an abandoned slate mine called La Bouche Noire (The Black Mouth). The mine had been sealed in 1958 after "a psychological event."

The film had no jumpscares. That was the horror. It simply unfolded —like a lung turning inside out. By the 47th minute, the screen went completely black. Not a technical glitch. A slow, deliberate fade. And then, the subtitle appeared: