“ 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.”
“ Whilst exploring underground the PCs discover tube like tunnels stretching for miles, upon further inspection the strange tunnels seem to connect all major cities in the are, what is their purpose?”
“ A certain type of toads, only found in the bleak swamps of Mournmist start falling on the city where the PC's are, like rain. Why?”