Butcher Block is a weekly series celebrating horror’s most extreme films and the minds behind them. Dedicated to graphic gore and splatter, each week will explore the dark, the disturbed, and the depraved in horror, and the blood and guts involved. For the films that use special effects of gore as an art form, and the fans that revel in the carnage, this series is for you.

Comparatively speaking, Neil Marshall’s widely-regarded survival horror film isn’t nearly as depraved, disturbing, or graphically gory as many of the movies featured on this column. It’s still worthy of inclusion in this particular space, though, for its unrelenting viciousness and high-level intensity that refuses to ease up. The Descent turns survival horror into a savage battle for the ages, and the deaths are just as brutal and bloody.

For his sophomore feature effort, Marshall wanted to scare the pants off of audiences. He felt his debut, Dog Soldiers, offered a lot of humor to offset the action and tension; The Descent needed to be through and through scary. A simple premise involving a group of six friends embarking on a cave adventure in the Appalachian Mountains becomes increasingly complicated, by design.

The opening sequence sets up everything, from crucial character dynamics between Sarah (Shauna Macdonald) and her friend Juno (Natalie Mendoza) to establishing the film’s tone. Sarah’s husband and daughter pick her up after a whitewater rafting trip among friends. The exchange of looks between Juno and Sarah’s husband lets the viewer in on the dirty secret of betrayal. It’s only a matter of when Sarah will learn the truth. A sudden, shocking car crash prolongs the inevitable, though. It’s the jarring way Sarah’s family is ripped away from her in a split second that sets a precedent for the film’s unflinching and violent grasp of death.

Above all, the opening sets up the dual nature of the film’s title. Physically, these six women are descending into a cave toward their doom. Metaphorically, it’s Sarah’s descent into madness. The central plot is set one year after her heart-wrenching loss, and her friends coax her into the trip as a means of healing. She’s distant and aloof, a clear sign that she’s still in a fragile state of mind. Juno’s appetite for adventure, leading the group into an unexplored and unknown cave system, becomes the inciting event when the cave collapses. Group tensions rise, while the viewer sees glimpses of something lurking in the background. Once the first member falls, it quickly becomes an epic brawl for survival against the Crawlers.

Whether it’s the gnarly bone break from Holly’s (Nora-Jane Noone) fall or an accidental pickaxe to Beth’s (Alex Reid) throat, and more, special makeup effects designer Paul Hyett (Attack the Block, Eden Lake) and his team had a heavy workload. Particularly in the prosthetics department. Full body casts had to be made for a few of the actresses, and many separate limbs were created as well. For Holly’s nasty fall, a leg with silicone skin was crafted, with bone fragment pieces that could be inserted in the open wound. Blood was pumped through it, making the gross bone protrusion even more horrible.

Hyett also took Marshall’s initial drawings for the Crawlers and tweaked the design from there. Marshall’s initial concept for the creatures had huge bug-like eyes that didn’t test well on screen. Hyett made them more human-looking. Between the creature designs and the actors that portrayed them, like Craig Conway as Scar, the Crawlers are unnerving and memorable movie monsters.

Ultimately, witnessing the gruesome demises of her friends and a harrowing truth reveal culminates in Sarah’s mental breaking point. It’s marked by a literal baptism of blood and a lot of Crawler slaughter. The ending changes depending on which cut you watch, but the result is the same; it’s a bleak conclusion.

The bloodshed, the primitive and instinctual fight for survival, the fantastic scares, and the unique setting and characters make The Descent one of horror’s best.