So your PCs have won their quest, be it slaying a mighty dragon with a magical weapon of old, beating a crime boss, or vanquishing a mighty wizard or wight, and they have taken possession of the treasure. Chest after chest of gold and silver coins, gold bars, and every kind of jewel and gemstone is theirs for the taking. If they are not careful, they may find that their trouble has only just begun.
Near a major city, a mirror image of the place has appeared. This strange double is infested with hostile insectoid humanoids that appear to match the city folk in numbers and armaments. The humans’ diviners have determined that the secret of the city’s appearance can be found within the double’s college of magic, so heroes are needed to explore within this mirror city and discover what has drawn it from its distant realm. There isn’t much time to spare, as the bug folk find their mammalian counterparts unnatural and blasphemous, and plan to destroy them.