Thunder on the wind
The history of the Thunderer according to the oral traditions of the Hobgoblins were supposedly passed on by notable leaders of the clans to whom the Dragon occasionally confided.
The Thunderer was an ancient and abused Iron emperor Dragon. At a young age It’s Eyes and wings were bound with magic shackles to prevent it from using it’s magic by some humanoid culture beyond the Mountains. It was forced to fight in arenas for the amusement of it’s captors. As the Dragon grew the unyielding shackles caused the dragon much pain. It learned to focus it’s thoughts and during a great battle slew it’s master and killed all of the Human clans it could find.
It wandered for a time between worlds until it heard the war drums of Clan of Hrogu and leapt from the mountain clouds breathing thunder and lightening slaying their (strong but unfortunately incompetent) leaders. The Thunderer seized upon their minds and showed them it’s command of them and learned of the troubling men of the rich Valley.
From that day forward The divine Thunderer has united the Clans so that we may crush the men and make them serve us.