It was a tiny, small, inconsequential disc. Golden in color, simple in appearance, the talisman was far more dangerous than any could comprehend. Well ... almost anyone. The goblin servants of Neltharion, the Earth-Warder, created the object, and even they weren't truly aware of just how terrible that creation truly was. For the golden disc held not only the power to tear through the Burning Legion; it held the power to control every dragon, every flight in the world -- with the exception of Neltharion, of course.
For he would rule them all. The voices told him so and promised him glory above all creatures of the world, mortal or immortal, no matter how insignificant. The Burning Legion was simply an army of pests to be eliminated, as were the kaldorei; the War of the Ancients was a petty squabble marring the glorious moment of his ascension. It was only a matter of time.
The Dragon Soul was perhaps the most dangerous creation in existence, and it was held in the claws of a dragon that was most certainly completely insane.
Today's Know Your Lore contains some information regarding Thrall, Twilight of the Aspects, the 4.3 5-man dungeons and the Dragon Soul raid. If you're avoiding spoilers, I'd skip this for now.