Xorn were frequently tamed and controlled by the Dao of The Underland City to tunnel new pathways for their sprawling civilization to eventually overtake. Allowing the Xorn to eat any non-precious metals they found, the Dao used the Xorn's natural capabilities to efficiently and safely mine the Underhollow.
Xorns were strange elemental creatures which lived within the Northern Greypeak Mountains. Xorns were very odd-looking creatures. They had radially symmetrical bodies with a large mouth at the top surrounded by three long arms interspersed with their three eyes. Their wide, pebbly, and rocky bodies rested upon three stumpy legs. They had talons at the end of their arms. Smaller xorns were about 3 feet (0.91 meters) tall, but the oldest specimens could reach 8 feet (2.4 meters) in height and width and weighed as much as 9,000 pounds (4,100 kilograms).
Xorns were immune to the effects of fire and cold and were resistant to electricity. Like other elemental creatures such as their arch nemesis, the Urdunnir, xorns could travel through ground and stone as if it were water, leaving behind no tunnel at all. They always passed through the ground mouth-first. Xorns could sense the vibrations of other creatures in the earth and they could smell their food from 20 feet (6.1 meters) away. A xorn could smell magical metal from twice that distance.
Xorns were scavengers, and they consumed rocks, minerals, and gems. In fact, they could not digest meat at all, so they did not eat creatures typically. They only attacked to defend themselves, although they could be more aggressive if hungry and hunting for their inorganic food. If in groups, they would often send one of their number to negotiate for food. It was extremely likely that they would attack if their requests for food were not granted.