The Tunnelers Below are a fictional race created by Fritz Leiber for his short story The Terror From the Depths, and were later expanded upon by Chaosium in 1994 for their Call of Cthulhu role-playing game.
The Tunnelers Below are a race of worm-like creatures which are as long as humans and a thick as their thighs. Along their bodies are numerous pairs of tiny translucent wings, that continuously vibrate. Eyeless creatures with a circular mouth that is lined with shark-like teeth. Creatures that possess great psionic abilities, especially telepathy. Which they use to invade your dreams, steal the memories and thoughts of the unwilling, and communicate with spirits.
The Tunnelers have an insatiable lust for knowledge about the Mythos and are drawn to every aspect of the it. It is known that tunnelers congregate below strong sources of psychic power, mystical energy, and locations which have been most influenced by aliens. They have a web of caves that spans the planet, which even traverses far below the seabed. One of their favorite spots is underneath the sunken city of R'lyeh, glutting themselves on the death-dreams of Cthulhu.
The Tunnelers are not a hostile race, as long as they are not provoked. When angered or threatened, they attack with their maw of shark-like teeth or burrow beneath the target, creating fragile tunnels to collapse the structure. The primary threat they pose to humans is that they are continuously telepathically broadcasting Mythos concepts, findings, and knowledge. Unless the victim moves or the tunnelers are driven away, he or she will either be driven completely insane or die.