After nearly four decades of exposure, the ichor-dripping design of Ridley Scott’s 1979 sci-fi/horror classic Alien is the the rare monster concept that hasn’t had its effectiveness blunted by time. Now, a new video essay by YouTube critic Kristian Williams goes into detail about what makes it such an iconic design.

Some of what the video goes over is well-honed territory for horror and science-fiction fans. The titular alien was provided by H.R. Giger, a surrealist Swiss painter whose biomechanical design was adapted wholesale from a 1976 painting, Necronom. He created Alien‘s adaptation out of animal bones, condoms, and a real human skull.

Giger made the model out of animal bones, condoms, and a real human skull.

Giger had two things working in his favor when it came to realizing his design. The first was his outsider status. Since Giger had never worked in Hollywood before, he had no preconceptions about what a horror movie monster was “supposed” to look like. The second was his background. A trained industrial designer, Giger had the actual know-how to create physical props based upon his artwork that could hold up to the rigors of film production. The result was that Giger was able to realize his vision entirely without compromise: the final Alien design literally looks it just stepped out of one of Giger’s paintings.

But what specifically makes this design so compelling to viewers? One aspect is undoubtably the design’s fetishistic nature. Nearly every aspect of the Alien’s lifecycle is highly sexualized: the eggs the Nostromo crew find look profane and vaginal; the Facehuggers they hatch are flesh-colored throat rapers; the Chestbursters are a clear analogy of childbirth; and the Xenomorph itself has a head that resembles a profane, dentate-tipped phallus. All of this contributed to a design that Alien line producer Ivor Powell once said looked like “it could just as easily fuck you before it killed you,” something about as far from the conventions of Hollywood sci-fi monster design as you could find in 1979.

[Photo: © 2003 Twentieth Century Fox/via IMDB

Yet in his video, Kristian points out an overlooked reason why Giger’s design works so well. Namely, it’s understandable.

At no point in Alien does a character explain the xenomorph’s lifecycle, but viewers are still able to piece it together, because there’s a clear progression in each stage. From alien egg to full xenomorph, Giger’s designs articulate a deeply Freudian series of nightmares, understandable to all of us, on the intersection of sex, death, and monstrosity.

It actually shouldn’t work–a lesser film would need a talking head to explain the progression from facehugger to xenomorph–but Alien nails it. And as Ridley Scott’s execrable follow-up effort, Prometheus, well proves, just so much of that success is due to Giger.