Cult of the Dragon
One of the weirder villainous organizations in the Forgotten Realms setting for Dungeons & Dragons, the Cult of the Dragon is a mad cult made up of humanoids who have turned to worshipping dracoliches as incarnate gods and see it as their holy duty to both entice more dragons to undergo the lich transformation, which they are happy to help with, and to aid dracoliches in their various schemes. They were founded by Sammaster, a former Chosen of Mystra who went insane when he couldn't accept that he had mistranslated a prophecy about dragons coming to rule Faerûn after some great apocalypse when he claimed that it would instead result in the world being ruled by undead dragons. Sammaster became a Lich himself to try and make his vision come to reality and was ultimately destroyed as part of a foiled plan to exploit the Rage of Dragons, an event that makes up the Year of Rogue Dragons trilogy of novels.
Current Status
In 5e Tiamat provided the correct translation that it was not "Undead dragons sitting on thrones" but the "Dragons will Burninate everything, skeletonizing even every person sitting on a throne". This prompted the switch of the majority of the Cult from the worship from undead Dragons to living chromatic Dragons, including their Tiamat herself.
This burst of deific influence allowed Tiamat to move her Cultist flunkies to the Sword Coast, culminating in the module Rise of Tiamat, in which they tried to fill the prophesy and release Tiamat from hell. This went well as one might expect, and a strike team of high-level adventurers supported by the forces of the Lords' Alliance slam the door on that plan.
The status of the cult is currently divided between youths Tiamat seduced in trying to create a successful dragon apocalypse and the traditionalists that still believes that dracoliches are rad.