Karun, dark god of the Underworld, was the Goa'uld who took humans, from Northern Italy, and placed them on the planet P7J-989 by way of the Stargate, which came to be known as the "Eye of the Underworld" in the people's history. It is unknown why he placed them there, as the planet had few resources and was of little strategic value, but it was assumed to be for research purposes by Stargate Command.
He ruled over the people for centuries, but was eventually overthrown in what came to be known as the "War of the Gods". It is not known whether or not this was the Volsinii rebelling against their "god" or a System Lord choosing to make war on Karun, though the latter has more evidence to suggest it.
Karun's legacy would live on, however, as the people kept the legends of their "god" alive and indeed even named a toxic gas, Karun's Shroud, after him long after his death. (RPG: "Friends and Foes: Stargate Season Two")
- Karun on Wikipedia