Cult of Bone
Ancient beyond reckoning, dating from the Time of Eld, when Dragons were common throughout the world, the Cult of Bone existed for a singular purpose: to steal the power of the great Wyrms for the mortals that desired it. Acting as hands of the Beast, the Cult of Bone operated clandestinely throughout all of the ancient empires, always representing a great threat to the natural order.
Murder, blackmail, coercion - none of it was beyond them, as they searched for every advantage, always pursuing Draconic Ascension - and even succeeding now and again.
From the Cult of Bone came Bone Dragons - the essences of a dead dragon trapped within its own bones and forced to serve - and the Ritual of Undying, where its members bartered away their mortality for greater arcane might and the centuries of life required to pursue their goals - if the mockery of existence that resulted could be said to be living. Great constructs called Wracks defended their temples and were used as shock troops - and they were spoken of with great fear for a millennia.
They operated from cells they called "Temples", performing rituals that both called to the Beast and worked to advance their own personal power.
In the days leading to the Cataclysm, the Cult of Bone openly sided with the Warlord, and represented a very dangerous group of artificers who followed him as an avatar of the god that granted them their power.