The ritual site is a deep, dark, dank worship area in Point Lookout. The local swampfolk sacrifice unwary travelers, and keep a vessel full of blood surrounding the Krivbeknih, a very dark and mysterious tome. The mood is implied to be "satanic" by Marcella, and "none of your business" according to Obadiah Blackhall.
The ritual site is a subterranean complex used for worship by the swampfolk. The entrance to the ritual site will be labeled "burned-out basement" by the Pip-Boy when you are in the complex, and will be called by this name on the entry door. The entry to the cavern will be blocked by wooden planks until you obtain the quest The Dark Heart of Blackhall. Following a straight path through the cavern will lead you to a small pit, where you will find a small bubbling gas pit surrounded by skeletons and a safe which contains moonshine and a Stealth Boy. At the very bottom is the ritual chamber where the Krivbeknih can be found, as well as the ritual knife, a unique weapon. Be warned, taking the Krivbeknih or the ritual knife will cause several angry swampfolk to spawn behind you. It's recommended to use a Stealth Boy or Chinese stealth armor before taking either in order to avoid the ambush. While exploring, the player can hear the same eerie whispers heard in the virulent underchambers in the Dunwich Building.