Citadel of the Bloody Hand

The Citadel of the Bloody Hand was a notorious stronghold hidden high inside Mount Waterdeep and considered part of the upper Dungeon Level of Undermountain. Some insisted it should be called the Citadel of the Black Hand.

History
The Citadel of the Bloody Hand was first developed in the as a base of operations for a local thieves' guild—either the Shadow Thieves or the Thieves' Guild of Waterdeep. The thieves managed to secure the area against Undermountain's monsters and defended it with many traps, and named it for their guildmaster.

However, the thieves' guild was later run out of Waterdeep. The fate of their base afterward was unknown; it might've been abandoned, seized by the Lords of Waterdeep, or infested again by monsters.

However, by the 1360s DR, part of the Citadel of the Bloody Hand had been taken over by the Harpers and made part of Harpers' Hold. The rest was occupied by the City Guard, who walled off the head of the Falling Stair to block incursions from Undermountain to the dungeons of Castle Waterdeep.

Defenses
The Citadel of the Bloody Hand contained many lethal traps and wards left by the Shadow Thieves; some were repurposed to defend a passageway to Harpers' Hold. The area of Undermountain around it was also rife with traps and guardian creatures, as well as spy-holes and secret passages.

Under the City Guard, the Citadel was occupied by some 46 Guardsmen and a number of wizards and priests.