Glob
It is believed that creatures like the Glob once lived exclusively in water. But now, the Glob is sightless but very aggressive, it is believed that it sees by feeling the movement of the water droplets in the air of subterranean caves.
Booglin
Sentient molerats that lurk at the deepest parts of the earth. They carry powerful drills that can pierce the toughest of armors, and with a keen sense of smell, can even surprise foes through entire walls. If you hear them, run.
Axe Beak
Territorial birds with beaks shaped like an axe. They usually travel in packs, making them exponentially more dangerous if encountered at night or aggro'd during the day. However, try feeding some of them some meat, who knows what might happen?
Skeleton
Dual cleaver-wielding Undead, sturdier than the bow-wielding skeletons you're used to, these are not afraid to get up close and personal. They roam the surface and close beneath the surface.
Patriarch Spider and Brood Spider
The worst of the worst. The Patriarch can patiently rest on the ceilings of caves until an unfortunate prey comes sauntering along, when it'll launch into action. The Brood hide closeby Patriarch Spiders, until they burst into a cloud of toxic gas.