Elgon Mastal was a former Jedi Knight who was banished from the Old Republic for treading too close to the Dark Side. After roaming for several months, he found the Chiss and a man named Thrawn in particular. Later, he found two Chiss apprentices, Jorell and Trivas to train.
When Thrawn fell out of grace within the Chiss Ascendancy, Mastal was forced out along with a sizable following of Chiss supporters to create the Nulvarl Empire. Later, he was overthrown by his apprentices and killed.