- Enter the Sanctuary.
- Assist the survivors.
- Hide in the Night Mother’s coffin.
- Kill the traitor.
- Return to the Night Mother.
There should be several guards outside the sanctuary when you approach it. Deal with them and head inside the sanctuary.
When you enter the Sanctuary, you will notice the entire place is on fire and structurally unsound. Close to the entrance, you will overhear two members of Penitus Oculatus discussing who among the Dark Brotherhood turned traitor. Neither of them knows the answer. After their conversation they head towards you. Deal with them as you see fit.
Astrid’s and Arnbjonr’s room is empty, so head down the stairs into the central room of the sanctuary. You will find Arnbjorn in his werewolf form, fighting Penitus Oculatus agents. You can try to help him, but his death is scripted. There is no way for you to save him.
Continue through the sanctuary, avoiding the flames until you find Nazir. When you find him he is locked in a duel with one of the agents. Assist him by killing his attacker and talk to him. His concerns that you might be the traitor are erased when you save him. Follow him in his search for an escape.
As you follow him as he searches for an way to escape, you should run past the room with the Night Mother. She will call out to you, telling you the only safe place is in her coffin. Make sure Nazir is out of combat, then run and open the Night Mother’s coffin. Walk into it, and it will close around you.
In the darkness of the coffin you will hear explosions and sounds of the sanctuary coming down around you. After they end, you will hear the voices of Nazir and Babette talking as Nazir tries to unearth you. When Nazir opens the coffin you find yourself in the main room of the sanctuary. Apparently, in the explosions, the coffin was thrown through stained glass window and traveled considerable distance.
After you step out of the coffin and talk to the survivors, the Night Mother will talk to you once again and inform you that Astrid is still alive. She will ask you to find her. Nazir and Babette will follow you after you inform them of what you’ve just heard. Take the stairs up to Astrid’s old chambers and you will see a horrifically burned Astrid stretched out on the floor in her hidden chamber, with candles surrounding her. She has performed the Black Sacrament, prayed to the Night Mother and placed herself in the center of the ritual.
Astrid reveals that she is the traitor. She betrayed you because she wanted things to go back to normal with the Dark Brotherhood. She was skeptical of Cicero and the Night Mother and jealous of you for being named the Listener. With her last moments, burned and dying, she performed the Black Sacrament on herself and asked for a contract. When you arrive her skepticism of the Night Mother is gone, since she knows that her prayers were heard. She reveals that what she prayed for was a mercy killing. She wants to be put out of her misery. She gives you her dagger, the Blade of Woe. Take it and kill Astrid.
After you kill Astrid, Nazir and Babette will comment on her death with anger and pity for their former leader.