The Avvar believe the caves to be carved by one of their gods, Korth. Following a tragedy, as Ruadan was grieving, he caused the caves to collapse, which was not taken very well by his fellow tribesmen, as he destroyed what they thought a gift from their gods.
Sometime later he chased Kaelah, his fellow tribeswoman, further into the caves, reaching the Deep Roads. As Kaelah prayed to Korth, dwarves appeared and saved her, which she took as a gift from the Mountain-Father. Ruadan was forced to escape.
He got stuck somewhere in the Deep Roads, and the darkness made him crazy, but also powerful. He gained powers to control other people, and used it to turn the Avvar warriors against their own tribesmen. It is possible he became a blood mage and this is how he influenced the warriors to do his bidding.
Some unknown time later Kiveal, an Avvar, reached the dwarves to ask them for help. With their assistance they bound Ruadan in the Deep Roads.