In the far reaches of a long-lost wilderness, there stands a forgotten town inhabited only by children. Though they appear normal enough, their eyes burn with madness, and they speak in a foreign, archaic tongue. Nearly a millenia ago, a powerful spell had gone awry, or maybe it had succeeded - in any case, it ended up blessing, or cursing, an entire generation of children with agelessness. However, as the centuries passed, the children's parents grew old and died, the buildings of the town crumbled to earth, and even the civilization itself faded into history, becoming lost to time. All that remained were the children, driven mad by the psychological toll of living for hundreds of years beyond their age. In time, most children died, killed off by fighting amongst themselves, while many others were driven to suicide. Only a small handful remain, and they are a strange people indeed.
Except, it doesn't have to be. Nighttime can be a relaxing, peaceful time in the world, when nature rests and soft shadows cover the ground. Not every night has to be filled with vampires, ghosts, beasts, and things jumping out from dark places.
A world based not on light and dark in conflict, but light and dark in balance. A world governed by a giver and a taker, rather than a creator and a destroyer. A world where evil is as much a corruption of light as it is darkness. Conflict arises out of a will to upset the balance.
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.