"Animated birds flap and shift over the cloak's folds and ruffles. A myriad of species, sizes and colors."
Its name comes from the mercurial, a robot with an ability to teleport itself randomly when hit; much like the cloak does to the player. It requires power which it consumes every time the player is teleported.
It is generally useful to all kinds of characters, as it gives an easy if a bit chancy, way out of a dangerous situation. All you need to do is to spend one turn putting the cloak on and then take it off when you are out of danger. Though it should be noted and emphasized that random teleportation might not always work in your favour and so could potentially cause the player character to teleport into a much worse situation.