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[edit]
In Dungeons & Dragons 5th Edition, the Cult has come under new management. Originally largely neutral towards the Dragon Gods, if on good terms with the Falazure portion of Null, in 5e Tiamat has attempted to subvert the Cult and bend it to her will. With Sammaster destroyed and unable to enforce his vision of the cult's missive, Tiamat has been able to sway significant portions of the Cult to instead revering Chromatic Dragons as living avatars of destruction, with herself as the pinnacle of everything that makes the chromatics divine, by asserting that the true translation of the prophecy is more along the lines of "dragons will rise up and strike down all who sit upon the thrones of the world, taking their rightful place as its rulers". There are still believers of the old guard around, and the Cult is actually fighting an internal war between old guard and new believers, but the main focus is on the Tiamat-worshippers.
This iteration of the Cult serves as the main antagonist in the adventure module Rise of Tiamat, which is all about the Cult of the Dragon trying to open a portal to Baator and release Tiamat onto the Forgotten Realms, similar to Takhisis. Canoticly, with every module since then that referenced it, 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.