From publisher blurb:
Your adventures have taken you to strange places before, but in the eyes of your experienced party, few of these places are as unusual as the bizarre Land Beyond the Magic Mirror. Here the delightful and the light-hearted often hide great challenges and dangers; here you will journey through a landscape unique among fantasy role-playing scenarios.
This adventure was first conceived by E. Gary Gygax as part of the Greyhawk Castle dungeon complex and has been the source of challenge and fun for many skilled players of the Advanced Dungeons & Dragons game. It is finally available to all players and can be added to your existing campaign with ease.
"The Land Beyond the Magic Mirror" is designed so that it may be used with its companion scenario, EX1: "Dungeonland." Still, "Land Beyond the Magic Mirror" may easily be played on its own, and should offer hours of excitement in its strange landscape!