"Did I? Well, it's so. My dreams are not like yours, Ser Duncan. Mine are true. They frighten me. You frighten me. I dreamed of you and a dead dragon, you see. A great beast, huge, with wings so large they could cover this meadow. It had fallen on top of you, but you were alive and the dragon was dead."
As becomes clear later in the story, the dead dragon proves to be Baelor Breakspear, who is killed fighting on behalf of Ser Duncan the Tall in a trial of seven.