The Brill Hounds was a group of thieves and bandits that operated out of the township of Brill in the years before the Third War. The leaders were Miracira Delane and her second-in-command Jonas Horrigan. They were known for quick in-and-outs in the businesses and establishments in Lordaeron's capital city. However, they were most infamous for a botched attempted robbery of the cathedral in Lordaeron, during which several priests were killed. Delane was arrested and the remaining Hounds were scattered.
The very next day, the Scourge came to Lordaeron. Most of the Hounds either succumbed to the Scourge or were killed. The survivors helped to free Miracira from prison and flee southward toward Stormwind, where they attempted to operate independently for some time but eventually joined with the Defias Brotherhood.
The Hounds exists as a Forsaken organization, comprised entirely of the undead and led by Horrigan. They act as spies and assassins for the Dark Lady rather than thieves.