The Second Sin
Thedas is a land of fierce diversity, from the assassin-princes of Antiva to the faded griffons of the Anderfels, but in my travels, I have found one tale that unites the people of this land. It is a story of pride and damnation, and although the telling differs, the essence of the tale remains the same.
At the height of its power, the Tevinter Imperium stretched over much of Thedas, uniting the known world under the rule of the tyrannical magisters. It is said that the Old Gods whom the magisters worshipped gave them the knowledge of blood magic, and the magisters used this forbidden power to cement their rule. The blood of elven slaves and humans alike ran down imperial altars to fuel magister greed, the tales of their excesses so horrifying that one can only be grateful that blood magic is prohibited today.
But all that stands tall must eventually fall. Perhaps they foresaw their ruin, or perhaps their pride knew no bounds, but whatever the reason, the magisters dared to open a magical portal into the Golden City at the heart of the Fade. They sought to usurp the Maker's throne, long left unattended in the Golden City after the Maker turned His back on His creations. They would storm heaven itself with their power and become as gods.
According to most versions of the tale, the magisters did indeed reach the Golden City and walked into the home of the Maker, where no living being before them had dared, or been able, to tread. But humanity is not meant to walk in heaven. The magisters were wicked with pride and other sins, and their presence tainted the Golden City. What once was a perfect, holy citadel became a twisted home of darkness and nightmares. The magisters were expelled back through their gateway and cursed for their treachery. As the Golden City had been tainted, so were the magisters twisted and transformed into things of darkness—the very first of the darkspawn. The Golden City, once a shining beacon at the heart of the Fade, became the Black City, a reminder of all that man's pride has cost.
—From Tales of the Destruction of Thedas, by Brother Genitivi, Chantry Scholar