Meet Mercer Frey outside Snow Veil Sanctum. Talk to him, and he will unlock the door. Enter it and fight through the draugr with him. There will be a larceny target on a trapped pressure plate: the Model Ship which can be sold to Delvin for a leveled amount of gold (300-800).
After finding a Word Wall (Disarm), the way will be blocked by a locked puzzle door, which usually requires a dragon claw made out of a specific material; however, this time Mercer will open it. After passing through the door, the Dragonborn will be shot by a poisoned arrow and fall to the floor, they will be able to watch Mercer's and Karliah's meeting and learn more about his real intentions. After their talk, Mercer will approach the Dragonborn and state that he will give Brynjolf their regards and stab them, and the screen will then black out. Hours later, the Dragonborn wakes up outside the Sanctum in a makeshift camp, where Karliah has been nursing them. Speak to her, and she will reveal Mercer's treachery to the guild and she will state that she found Gallus's journal but it is written in a strange language and that it needs to be translated . This will end the quest and start the next one.
I'm on my way to meet Mercer Frey at the ruins of Snow Veil Sanctum, Karliah's last known location. Together, Mercer and I intend to hunt her down and make her pay for Gallus's murder.
The tables have unexpectedly turned, and Mercer Frey has been revealed as Gallus's killer. I now find myself in Karliah's care after Mercer tried to murder me, claiming I'd outlasted my usefulness by witnessing their conversation. I've also discovered that Mercer, Gallus and Karliah were members of some sort of group calling themselves "The Nightingales" - guardians in service to the goddess Nocturnal. What they're protecting or what this has to do with the Guild is still a mystery to me.
- If Mercer does not move, he can be pushed into Snow Veil Sanctum with Unrelenting Force, then into the door by walking into him.
- Mercer cannot be pickpocketed until after he opens the final puzzle door, and after that his Dwarven Sword of Devouring may be taken (with the Misdirection perk). If this is done, the dialogue and animation still follow, but he threatens Karliah with his fists and cuts the Dragonborn with an imaginary blade.
- After Mercer Frey unlocks the puzzle door, he can be taken back to the previous pull chain activated gate and locked out. Karliah will still shoot the Dragonborn with the poisoned arrow. The dialogue will follow but Mercer Frey will not be present.
- Snow Veil Sanctum has a few tripwire-based traps.
- Snow Veil Sanctum is on the Dungeon Lock Outs list.
- The final room in which Karliah is first encountered contains the skeleton of Gallus. This is proven if you talk to Mercer Frey before entering the crypt. He says that he was attacked by Karliah, Karliah killed Gallus and then threw his body down the shaft that goes into the final room.
- Mercer Frey actually probably killed Gallus then threw his body down the tunnel.
- In the same room as the word wall, there is a skill book, Ice and Chitin, for light armor.
- Being shot by Karliah is scripted and cannot be avoided.
- It is possible to get Mercer's sword early. In the Word Wall room, three draugr will wake. At least one of these draugr can, and will, use the Disarm Shout. Lure him to Mercer, and if the draugr does use it on Mercer, his sword will go flying, allowing it to be retrieved.
- If the above happens, Mercer will never get his sword back. This makes fighting him in a later quest much easier, as he will only have a steel dagger.
- Mercer's comment, "You're pretty noisy for someone who calls himself a thief," seems to be unrelated to Sneak level, as he may comment this even to those with maxed out Sneak.
This section contains bugs related to Speaking With Silence. Before adding a bug to this list, consider the following:
Sometimes Mercer Frey does not immediately unlock the door to Snow Veil Sanctum. This can sometimes be fixed by saving and reloading, although that is not always the case. This can also be fixed by traveling to another location and then traveling back (with him as your follower). Also, make sure to get rid of any followers before getting anywhere near Mercer.
- Console command for unlock can fix this.
- The game may freeze during the cut-scene with Karliah (for fix see talk page.)
- Waiting for a number of hours may fix this.
- Karliah may become stuck inside Snow Veil Sanctum.
- After the cut-scene where Mercer stabs the Dragonborn, the camera will be zoomed to first person and stuck there.
- A solution may be saving and reloading.
- Another solution to this bug is by turning into a werewolf: when the effect wears off, the Dragonborn will be able to go to third and first person as usual.
tcfreecam would also fix this bug. Console Command
- The floor may be missing random chunks, causing Mercer to fall in.
- Attacking Mercer before he opens the Dragon Claw door may cause him to become hostile when interacting, as well as when you enter the corridor leading to the door.
- Re-entering the room will fix this, allowing the player to interact normally again.
- If you have been kicked out of the Thieves Guild by either provoking a member or provoking Maven, Mercer won't begin the quest by beginning the dialogue.