Yesterday I confronted the archdemon
who was leading a darkspawn invasion of Ferelden. Its army was sacking the capital of Denerim. My party rushed to the top of Fort Drakon, where the archdemon was perched. We attacked and brutal battle ensued. The fight was not going well, but then I noticed a ballista on the battlements. I swung it around and loosed bolts upon the dragon until it lay dead.
In the end, I saved Ferelden, and got the girl.