Shaft Abominations

The furrow carved apart the tall grass like a scar in the earth itself. Göcer's horse kicked at the ground, her head turned to the side. She didn't want to be here. Her ears turned. Chief Erkiner called a halt. Sergen dismounted, but nobody else did. Some of the hunters allowed their steeds sideways steps back and forth. Göcer's horse stayed still.
Sergen opened his pack, and placed the firemaker on the ground. When the blast jolted the worm from the ground would the hardest moment. Sergen reached for tinder, and then the ground exploded.
Dirt showered the man, and for a moment Göcer thought he had been swallowed. Instead, the Worm had burst out a dozen meters away. Sergen's horse bolted first as the man clambered to his feet, running after. The others followed. Göcer's bolted right, and he leaned in to stay in saddle. The gaping void of the beast's maw rumbled, and someone loosed the first arrow. Göcer pressed hard into the side of his steed, and she turned, still at gallop. He drew his bow, loosing it at the monster. Sergen was still running for his life, and after his horse. The worm turned as Erkiner yelled over the cacophony. Gather behind the worm, fire again, turn left.
The worm smashed into the ground, burrowing halfway in before emerging again. Half the riders had not even loosed an arrow before their horses had already turned again. Sergen had managed to remount, and rode alone some 200 meters away. Göcer loosed another arrow.
He had no idea if he even hurt it.

The works of the shaftbuilders dot the known world, huge underground complexes buried underground by the long millennia. Treasure troves of lost knowledge, would-be archeologists and treasure seekers have to contend with not only finding these places, but also the monsters that are released the moment someone digs their way into a shaftbuilder site. Not a true species, shaft abominations come in infinite varieties. Their commonalities are their inexplicable presence in shaftbuilder sites, ability to survive in places where reason would dictate no great predator can find sufficient nourishment, extreme hostility to almost every living thing, and a general innate understanding that their very presence is an affront to nature itself.

Basic Information

Anatomy

Few commonalities exist in the appearances of these monsters. Some are massive, dwarfing men many times over. Others are much smaller but no less vicious. Some have 8 legs, others have none at all. Some appear as vile parodies of regular beasts, while others follow nothing but their own bizarre patterns. In general, fur is rare, and many of these creatures have been observed to be slimy and have underground coloration, lacking pigment and appearing pale gray more often than not. Almost all are equipped for predation, sporting a powerful maw, claws, or another weapon. A few even have strange magical powers.

Ecology and Habitats

Named shaft abominations for their tendency to lair in shaftbuilder sites, these creatures do not have a clear ecological niche. Though certainly willing and able to devour anything they come across, these creatures are often the only large creatures that emerge from the ground when a shaftbuilder site is uncovered. The question then arises as to whether these creatures were simply in hibernation or if they do not need to eat like regular beasts. When loosed on the countryside these creatures make short work of local wildlife, often attacking livestock or even the settlements of regular folk. These rampages continue until locals organize hunting parties and kill the abomination.