Off the set and out of character, Hollywood legend Lon Chaney was a handsome and effortlessly charming man, with a broad chin, jet black hair, and debonair style. On set and in the early days of the movies, he was often barely recognizable—and utterly, utterly terrifying.

As well as being an actor, writer, and director, Chaney was an expert in makeup and special effects, and in the 1920s and 30s used his extraordinary talents to portray many of cinema’s most terrifying characters, including the Wolf Man, the Hunchback of Notre Dame, and a memorably creepy hypnotist in the classic early horror movie London After Midnight.

Of all of his roles, however, perhaps Chaney’s most terrifying was as the title character in 1925’s Phantom of the Opera.

Chaney’s grotesque appearance in the movie was achieved using egg membrane to give his eyes a misty, clouded look; using strips of fish skin to pull his nose up, with their edges hidden under a bald cap and straggly wig; building up his cheekbones and chin with cotton balls; and using actors’ greasepaint to darken and contour the remainder of his face.

His shocking appearance was reportedly kept a close secret, both during and after filming. The movie’s distributors prohibited the Phantom’s face from being shown in any previews or promotional material, to keep its final reveal in the movie as much of a surprise as possible, while on set Chaney’s makeup was not revealed until the day it was required.

(Allegedly, Chaney tested out the look out on an unsuspecting cameraman by unwittingly summoning him to his dressing room and then confronting him in full Phantom makeup. “I almost wet my pants,” the cameraman later recalled. “I fell back over a stool and landed flat on my back!”)

It certainly proved an effectively terrifying look, but Chaney’s horrific Phantom of the Opera makeup did not come easy. In some close-up scenes, the Phantom’s grotesque appearance was reportedly achieved by holding his face in place using a makeshift system of metal wires and rubber. But after a long day of filming and contorting his face into all manner of horrific expressions while wearing it, the device would cut into Chaney’s skin, causing a great deal of pain and often considerable bleeding.

Ever the professional, however, Chaney simply patched the injuries up himself, and continued with the movie!