Subterran

The Subterrans are a subterranean race from Earth.

Physiology
They are grey, motley skinned beings with white-washed eyes.

History
The Four presumably encountered the Subterrans and stuffed and mounted their carcasses in their trophy room. When Elijah Snow infiltrated their base he was visibly disgusted at the display.

Source

 * Planetary 006 (1999)