Night of the Hornéd God

There's an alternate universe right beneath our feet, a universe of basements and sub-basements, steam tunnels, catacombs, subways and sewers. And it's inhabited. By the homeless, the forgotten, the disenfranchised. And something else. Something evil, called up from he furthest reaches of Hell to prey on the living and the dead alike on the Night of the Hornéd God.