A Collar of Coercion is an item of steel construction, held together by rivets, and hexagonal or roughly oval in shape. Hinged on one side, it can be opened and then closed again around a humanoid neck and locked.
A long lever with a handle at the top and a cast iron key at the bottom is used with these collars - the key-like end of the lever is inserted into a second, larger keyhole on the collar, and by grabbing and twisting the handle, springs are tightened and set inside the steel construction. These work to power various types of mechanisms which are designed to coerce the collar wearer into carrying out actions against their will, or more simply, to force them into slavery.
There are different types of these collars, but all involve mechanisms which will prove fatal or extremely painful to the wearer unless someone rewinds the springs at regular intervals. The wearers themselves cannot turn the long lever used for this purpose.
For example, in one design, the springs in the collar will slowly unwind - as this happens, daggers will slowly protrude from the collar into the empty space at the center of it, eventually piercing and killing the wearer. In another version, only a single, poison tipped metal thorn protrudes which accomplishes the same task. In yet another design, through a serious of clever gears, a long blade will suddenly spring forth into the center of the collar, completely decapitating the wearer if the springs are not tightly recoiled every ten hours.
Through the use of these collars, the wearers can be turned into hand maidens of evil, carrying out various short activities under threat of their own demise.
Notes: Because what dungeon is complete without a slave in a collar? I see this item as something I'd be most likely to use with an NPC, to compel them to commit evil acts in the service of an evil master. I wish I could say that this wasn't inspired by a similar, real-life contraption... please forgive the crude sketch!
Hero Games - Star Hero
3 hours ago