AgMemdius was a Skotl dragon living before the Age of Fire, who fought during the Dragon Civil Wars.
He was known to have engaged in aerial fight with NeStirrath and while most dragons were satisfied to cripple a wing of an opponent, AgMemdius wounded both the wings of NeStirrath to cause him to fall to his death. However FeHazathant intercepted NeStirrath's fall and saved his life.
From NeStirrath's song, it's implied AgMemdius was responsible both for the death of his mate Esthea and the murdering of their hatchlings.
AgMemdius himself was told to have perished by NeStirrath's flames, during the same bloody battle that left NeStirrath crippled.