The Mace of Molag Bal is one of the Daedric artifact weapons in The Elder Scrolls V: Skyrim, and finding it is one of the darkest and most memorable quests the game has to offer. As a weapon imbued by the Daedric Prince of Domination, it traps the souls of everything the player kills with it, providing a great way for non-magic users to fill soul gems for enchanting.
To obtain the Mace of Molag Bal in Skyrim, the player must head to the city of Markarth. Along one of the city's many winding sidewalks, they'll encounter Tyranus, a Vigilant of Stendarr who is investigating a strange home in the city. He will ask the player to help him search the abode; agreeing to assist begins the quest, "The House of Horrors." While this quest isn't one of the hardest quests in Skyrim, it is one of the most sinister.
Once inside, the voice of Molag Bal demands that the Dragonborn kill Tyranus. If the player tries to leave, the Daedric Prince commands Tryanus to kill you as well. Objects begin to fly violently throughout the house, making Tyranus fear for his life and attack the Dragonborn. After the Vigilant is defeated, Molag Bal invites the player into the chamber below the house.
Freeing Logrolf the Willful in Skyrim's "The House of Horrors" Quest
At a shrine in the basement, the Daedric Prince offers his mace as a reward, but before the player can actually pick it up, spikes spring from the floor and form a cage. Molag Bal offers the Dragonborn another deal. A priest of the Daedric Lord's rival Boethia was previously desecrating the shrine, but has stopped coming after being captured. The player is tasked with freeing the priest Logrolf the Willful so he will return to the shrine and give Molag Bal the chance to enslave his soul. The player will be set free even if they refuse, but the only way to get the mace is by helping the Daedric Lord achieve his insidious goal: perhaps starting the Dragonborn down a path of theft and murder.
Logrolf is imprisoned in a Forsworn camp somewhere in the Reach. Unlike many of the hidden and scripted locations in the game, the exact camp holding Logrolf is random. If the player has already wiped out the camp he happens to spawn in, he'll immediately make his way back to the shrine in Markarth.
Alternatively, the Forsworn at the camp may not be hostile to the player depending on if and how they completed "No One Escapes Cidhna Mine," another quest in Markarth. Otherwise, the Dragonborn must sneak or fight their way through the Forsworn camp where Logrolf is captured. After freeing him, the Boethia priest will be less than thankful and rush off to desecrate Molag Bal's shrine once more.
Arriving at the house, the player should follow Logrolf down into the basement. At the shrine, he will be trapped in the spike cage, and Molag Bal will hand over the mace to the player; however, it is disenchanted. As Logrolf refuses to bend the knee, the Daedric Lord commands the player to kill him with the mace. After Logrolf is slain, Molag Bal resurrects the Boethian priest and instructs the Dragonborn to repeat the process until he relents, pledging his soul to the Prince of Domination. The player is finally commanded to kill Logrolf once and for all. Accomplishing this, Molag Bal will bestow the Dragonborn with the mace, now fully enchanted and able to capture souls. The "House of Horrors" quest is complete. It's one of the most disturbing in the game unless players mod Skyrim to be even more horrifying.
Skyrim is available on PC, Xbox One, Xbox Series X/S, PlayStation 4, PlayStation 5, and the Nintendo Switch.