Unseen

The Unseen were a group of shapechangers, illusionists, assassins, thieves and evil creatures based out of Waterdeep. They were led by a greater doppelganger known as Hlaavin, who masqueraded as the Masked Lord, Nindil Jalbuck.

History
Originally a band of dopplegangers controlled by illithids, known by that species as a druuth. They were tasked with spying on Waterdeep for the Underdark city Ch'Chitl but when the elder brain of that city died, control of the druuth was lost. One of the dopplegangers was secretly half-illithid so this creature, called Hlaavin, took control.

Originally based in the Rat Hills, the Rat Hills Conflagration forced the group wholly into the city. They set themselves up in the Hanging Lantern, a high-class brothel that catered to the nobility and the wealthy where they used their abilities to glean secrets from their clientele until the famous writer Volothamp Geddarm revealed their ruse. The group spread out after that, creating several bases and outposts in Waterdeep's sewers and Skullport as well as one in the Dungeon of the Crypt.

Several notable setbacks had been documented but only a few of their successes had become known outside of the organization such as the transportation of the creatures known as the wilora into Waterdeep. The rest remained secret such as their inroads into the Arcane Brotherhood, the discovery of the identity of the leader of the Red Sashes and the supplanting of one of Waterdeep's Masked Lords.