Quest: The House of Horrors
Reward: Mace of Molag Bal
Location: Abandoned House in Markarth
Prerequisite: Leave Markarth then return
Go to Markarth.
Walk up the street a little bit, you will see two people talking about a haunted house. You then will be asked if you know anything about the house. Once you've talked to Tyranus you will start the quest House of Horrors.
Follow Tyranus into the Abandoned house.
Once you've searched the house a little bit he will ask you to try to open a door, it won't open. You'll be locked inside the house.
Molag Bal will start talking.
Tyranus will turn hostile, you must kill him to get your reward.
Go back down to where that door was locked, it will now be open.
Once you're down there you will see your reward (Rusty Mace)
Go up to the mace.
Molag will tell you to find the Priest of Boethiah
He will be at a random location, it is different for some people. It will show you a marker so he is pretty easy to find.
You'll have to fight through a couple Bandits or Forsworn.
Once your at the location, you will find Logrolf the Willfull the priest your looking for.
If you can try to Persuade him that Boethiah sent you. Or intimidate him by saying Molag Bal sent you. Once you've done that untie him and meet him back at the Abandoned House.
He will pray at the altar, Molag will trap him.
Beat Logrolf into submission.
You'll Get the Mace.
Once Logrolf submits you will have to kill him.
The Mace of Molag Bal is yours.