Voors

The Voors were a powerful and prosperous race of dwarves, predating humankind. Driven underground by the Hyperboreans and humans, they evolved into blind, albino creatures.

In the RPG...

Though similar to Martense Kin, the Voors are far more adapted to underground life. As such, if a Keeper were looking for an underground foe, I think the Voor would be the better choice. They are also not limited to a single location. I personally think they are much more terrifying, too.

    The Voor tend to swarm their enemies in combat, but a lone Voor may try to sneak up on a target and strangle them. Thankfully they aren't very strong, so an average human has an 81% chance of breaking free.

In a video game...

I think the Voors would make for great enemies in a game. They're suitably horrific in appearance, could potentially pop up anywhere there is dirt, and only take a couple of bullets to kill. They're also said to swarm, so any encounter could be escalated if need be.

In a film...

As I've said, I think the Voors would look absolutely terrifying... if done right of course. They lack pigment, and in the source material are compared to worms, which makes me think their skin is also a little translucent, which would be even more disturbing. Story-wise, their subterranean lifestyles remind me of The Descent, though I think they could be inserted into any plot involving excavation, not just caves.