An Ergastulum is a building used to hold in chains dangerous slaves, or to punish other slaves. The Ergastulum is subsurface and large enough to allow the slaves to work within it and containing narrow spaces in which they sleep.
Sometimes I create a lot of things behind the scenes that go un-shown but this was a fun little test I did the past week.
I've always had a vision of using Silver Bullets against the Werewolves in the game but had to make sure it was approached carefully without ruining the atmosphere.