From the back cover:
It's a mirror of life trapping, isn't it?
Well, yes and no. People go in, and they don't come out. Nor can you talk with anyone inside. Somehow, that's not quite the way you remember those mirrors work.
This Skarda fellow showed up a few years ago with a band of raiders, and no one in the land has been safe since then. Whole villages have disappeared into this Skarda's mirror. Your band is approached by relatives of one of the victims - an adventurer like yourselves.
You have to get that mirror of whatever-it-is, find this man, and get him out in one piece. The reward is more than adequate. Only problem is, no one out here can tell you what to expect once you get in - or even how to get there.