From publisher blurb:
While adventuring though a dungeon, the players find what appears to be a small set of closed black curtains mounted upon a wall. Drawing the curtains aside the players find a mirror which promptly sucks them through to its other side. There the players find a maze like hall of magical mirrors that they must carefully navigate to find their way to freedom.
Characters peering into this mirror will spy a black-cloaked figure seemingly sneaking around behind their reflection. This mirror will steal one item at random from anyone passing through it. The item is either lost forever or turns up later among the treasure found in another room within the complex, possibly one set up for the sole purpose of storing the stolen objects.
A line of unique and challenging chambers, designed to be dropped into an already existing adventure; Add-A-Rooms are quick and easy ways to add a little something extra to your game. Each Add-A-Room features elements that can be re-used in other adventures, such as magic pools, fake treasures, or ingenious traps.