Metaphysical / Paranormal event
Some say the awakening began due to some dwarves who mined into the earth a bit too deep. Some say that C.O.S.M. were playing with dark magics. And some think that chants of the frost giants were at fault. Regardless they awoke. Dragons of every color and variety marching their orcs across the land as they began to make attacks on cities and their military forces.
These attacks were largely a surprise to most. Catching nations off guard military forces were hard pressed to do anything about it. Atleast until the illithids joined into the battle. They made a deal with the other mortals to help defeat the dragon clan menace. The Silver dragon clan would later approach to also aid in this endeavor thus making them very disliked by the other dragon clans.