Heroes of the Zeroes is Nick Rogers’ daily, alphabetical look back at the 365 best films of 2000 to 2009.

A brutal, bone-crunching creature feature with marvelous subtext, Neil Marshall’s The Descent nightmarishly played out like an earthen black-box horror show.

In this 2005 film (released stateside in 2006) — Marshall’s breakthrough after Dog Soldiers — a sextet of female friends goes spelunking after a tragedy ripples through their social circle. Getting lost is their smallest worry, as bloodthirsty creatures — which have adapted frighteningly well to cave dwelling — stalk them.

What’s meant to become a claimant cave discovery — and, thus, reclamation of their friendship — instead becomes a death spiral. Bones don’t break, they jut. Lighting is all phosphorus flares, dimming flashlights and glowsticks. And the sound of the creatures’ gutturally clucking jaws creates instantaneous wincing. Tension is pitched at such a primal level that, at times, it’s barely bearable.

That’s because Marshall delivers what amounts to a feature-length exploitation of viewer phobias — distressingly claustrophobic and shot so vertiginously that it feels as though you’re dangling in the cave with the women.

The generously gelatinous gore isn’t without metaphorical purpose either. As the cave gets wormier and wetter, tighter and more terrifying, it feels like a womb thick with amniotic fluid. And the environment replicates their womanhood in a manner fraught with psychological interpretations.

Although Marshall’s attempt to justify the U.S. ending is admirable, the unrated, original ending is the only way to go — providing a chilling bookend to a motif and suggesting that what seems like cerulean-tinged peace is actually the solitary solace of madness.