Crawlers (The Descent)

Crawlers are the primary antagonists of the horror film, The Descent, as well as its sequel - they are a race of cave-dwelling humanoids who have adapted to near-constant darkness and lost any previous trace of humanity they may of had, becoming monsters in the process.

Biography
Crawlers are vicious humanoids who have existed for many years underground in a remote cave system which was undiscovered by the modern world, this allowed the Crawlers to breed and evolve in isolation from humanity - becoming monsters that would only ever leave the cave system during the night to hunt for food in the nearby forests.

When a group of female explorers disturb the Crawlers' cave system they become exposed to humanity for the first time in presumably centuries, resulting in a bloody confrontation as the Crawlers begin to hunt them down as potential prey - while in turn start to become hunted by the survivors, resulting in a war between the two factions.

Abilities
Crawlers are blind but can detect prey via sounds and echolocation, they are perfectly adapted to life underground and can climb walls with ease, move with great speed and have great strength - they are also vicious pack hunters who can work as individuals or as a group to hunt and take down prey : they are animalistic and thus have no real higher intellect beyond that of an intelligent animal.

Trivia

 * when designing the Crawlers the creators of the Descent wanted them to be in essence "cavemen that never left the caves" - thus their radical shift in evolution.
 * the Crawlers were hidden from the main cast until filming began, this way the shock the group have upon seeing the monsters was largely real.
 * the Crawlers were originally going to be exclusively male but the creators decided to add female and children Crawlers to show that it was an active colony, feeling having male-only Crawlers would make no sense as to how the colony would of survived.