The Ulgos were originally a people who had no god -- referred to as "the Godless Ones." They wandered and cried out unheard in the wastelands and wilderness of the West. One of their number, a just and righteous man named Gorim sought UL and eventually found him after twenty years of searching.
After persisting in seeking UL, UL relented and adopted the people of Gorim and became their god and these people became the Ulgos.
By the time of Garion, they live in subterranean dwellings and the capital of Ulgoland is Prolgu They have a fairly religious society and one of their caste are diviners, people who are able to detect caves and have the ability to pass through rock. Diviners are zealots.
Relg is an Ulgo with the ability to pass through rock.
Ulgos tended to be short but broad-shouldered, often with pale skin, colorless hair and dark eyes.