The Dark Heart of Blackhall

The Dark Heart of Blackhall is a side quest in the Fallout 3 add-on Point Lookout. The player character is tasked with finding Obadiah Blackhall's book, the Krivbeknih, which was stolen from him by some swampfolk.

Detailed walkthrough
Enter Blackhall Manor, where Obadiah will speak of a book that has been stolen from him and taken to the east, at the ritual site. Upon leaving Obadiah's home, the player character is met by Marcella, a missionary spreading her faith across the wastes. She claims that Obadiah actually wants the book for more than just keepsakes, and plans to use it for a ritual to control the swampfolk, and under no circumstances should it be returned to him. She requests that upon finding the book, it should be given to her instead, at the disaster relief outpost, in the western half of Point Lookout.

However, to make either decision, the Krivbeknih must first be found. Head to the ritual site and look out for the swampfolk guarding the entrance to the area. Look for a small door in the ground amongst the charred remains of a building and head in. Navigate through the chambers to the bottom of the ritual area where a mutilated body with a ritual knife thrust into its head, lying on top of a large table can be seen.

Directly behind the table is a pedestal with the book inside. Upon taking the book, swampfolk reinforcements will begin to pour into the area, furious with the attempted theft. It is likely to be ambushed by additional swampfolk upon leaving the basement. Once out and the area is clear, either return the book to Obadiah or bring it to Marcella.

If taking it to Marcella at the disaster relief outpost, the player character will discover that she was killed in her tent and may be ambushed by at least one smuggler. Obadiah apparently hired smugglers to kill her. In addition, "Die thief" is written in blood on the side of the tent.

There is a holotape in the same tent as Marcella. Upon listening to it, she begs the player character to destroy the Krivbeknih. If wishing to do so, the player character must venture to the Virulent Underchambers in the Dunwich Building, back in the Capital Wasteland. Access the part where there are metallic corridors near the end of the underchambers, and then ignore the exit stairs. Enter the lowest level into the tunnels beneath where Jaime can be found (if not previously killed) worshipping the obelisk. After finding the obelisk in the Dunwich Building, activate it and the book will ignite in flames and also incinerate the nearby feral ghouls.

If deciding to take the book to Obadiah, he'll reward the player character with 1000 caps. Nothing else changes - he will still go to the basement and pray, whether or not the book has been destroyed.

Reward

 * If giving The Krivbeknih to Obadiah Blackhall, the player character's reward is 1000 caps and 100 XP for completing the quest.
 * Alternatively, destroying the book with the Obelisk in the Dunwich Building will net positive Karma (500 points) and the same 100 XP.
 * Alternatively, the book can be given to Obadiah as the reward. He then can be killed for no Karma loss. The book can now be taken to the Dunwich building and destroyed or kept as a souvenir. It's one of the few unique items in the game that's actually unique in appearance as well as name.

Bugs

 * It appears that if you take the book from the ritual site and head to Blackhall Manor to return it, you will engage in a conversation with Obadiah Blackhall. If you tell him you haven't decided what you're going to do with the book, he will mention Marcella. You then will have the option to say she is dead, even if you have not visited her yet and seen her corpse.
 * It is possible that upon returning to the Capital Wasteland to finish the quest, the map marker will be located in the center of the map next to Springvale Elementary School instead of at the Dunwich Building, which is located in the bottom left corner of the map.
 * It is possible that Marcella won't show up dead in her tent, though the smugglers have conquered her camp. You can however use the console to manually update your questlog by using the command on the PC, where 'xx' must be replaced by the number the Point Lookout-DLC gets in your load order. Your questlog now lets you choose between helping Obadiah or Marcella.
 * This is caused by obtaining the Krivbeknih before speaking to Marcella in her tent. If the player speaks to her before obtaining the book or before starting the quest, she will appear in the tent after the smugglers attack. Only speaking to her outside Blackhall Manor after receiving the quest will prevent the bug.
 * Upon discovering the Krivbeknih in the underground shrine, the player will see that it is resting within a font. From most angles the font looks empty with the exception of a skull and the book itself. However, if the player is to view the font from certain angles it is actually filled with what is presumably blood, which disappears and reappears depending on the player's point of view.
 * For some people, listening to Marcella's holotape causes the game to crash. This makes it impossible to complete the quest in the method of "giving her the book instead of Blackhall" without using the console command "setstage".
 * Upon exiting the ritual site, the game sometimes crashes.
 * Marcella's safe may remain red after you find her dead in her tent, causing you to lose Karma even if you open the safe with her key.