The Wyrmsinger Sect are the cult dedicated to the Seer Unseeing in Vralkast. An argument could be made that the Wyrmsinger Sect is technically a Cult of the Dragon Below, as they worship a power within Khyber, but whilst the Seer Unseeing can be wrathful, she is not as malicious as many of Khyber's powers. The Wyrmpriests act as the Seer's fins and fingers in the city of Vralkast, instructions whispered directly into their ear canals.
They are secretive, but open. Everybody knows the Wyrmpriests exist and where to find them, but the nature of their deity or the exact forms of their worship are mysterious.