Before Chicago was a city, before the white man cleared the prairie and swamp to build their roads and towers, there was the pool. The pool had always been. A doorway to another place, a place filled with dark things seeking to enter our world. The Keepers of The Fire kept watch over the pool, keeping the Weendigo, the man-eaters at bay.
But the settlers came and the Keepers gave up their sacred charge, cursing the white man to deal with the dark things. Other guardians answered the call to protect man from the Weendigo, but they were too few and on too many full moons the dark things crept into our world unchecked. The man-eaters sought sanctuary from the day in the dark places, coming out only at night in search of meat or gold. They feared only the light of day, the flame of fire and the touch of cold iron.
Eventually the Weendigo became so great in the number that the shadow guardians of the city purged Chicago with a great fire. Many of the man-eaters perished. Still, some survived and hid, waiting for more full moons and an unguarded pool.
Now, the guardians of the pool are the unwanted of society. The ones no one will miss if snatched in the night to be Weendigo meat. Under the city they clash, the man-eaters and the forgotten Keepers.
This is Underneath.