Dumat

Dumat or the Dragon of Silence was the first among the Old Gods, said to be imprisoned underground by the Maker for usurping his worshipers. He was said to be the most powerful of the Old Gods and teacher of Archon Thalsin. Some time after their initial corruption, darkspawn burrowed into Dumat's underground prison, where the Old God was corrupted and transformed into the first archdemon. Dumat was slain at the Battle of the Silent Plains in 992 TE, approximately 1,000 years before Dragon Age: Origins.

In Dragon Age:Awakening, you can become the owner of the weapons that are rumored to have been made from the bones of the Archdemon: Dumat's Spine and Dumat's Claw