It is recommended that the Dragonborn is at a fairly high level for this quest, preferably level 20 or above.
Track down the Dunmer behind the Guild's misfortunes. Quest Giver:Mercer Frey Next Quest: Hard Answers Reward: Gallus' Encoded Journal, Word for the Disarm shout ID: TG05 Suggested Level: 62 more rows •
Mercer had the Skeleton Key. Which grants uncanny luck and the ability to open any lock to whomever possesses it. With the exception of the player, of course. So he opened the door with his key and the Skeleton Key or something along those lines.
Start the Thieves Guild at level 45+ for the best gear and the Dark Brotherhood can be started immediately. All the best items like the Blade of Woe and Ancient Shrouded aren't leveled so you can get them whenever.
Send a message to a former Thieves Guild client. Quest Giver:Brynjolf Concurrent Quest: Meet the Family Reward: Leveled gold ID: TG02 Suggested Level: 63 more rows •
Find the books needed to identify the artifact found in Saarthal. Quest Giver:Savos Aren Next Quest: Good Intentions Reward: Skill books ID: MG03 Suggested Level: 82 more rows •
Hard Answers is a Thieves' Guild quest received from Karliah after completing the quest Speaking with Silence.
Speaking With Silence is a quest available in The Elder Scrolls V: Skyrim. It is offered by Mercer Frey immediately upon completion of "Scoundrel's Folly" in which the Dragonborn must accompany Mercer Frey, guildmaster of the Thieves Guild to Snow Veil Sanctum to find and confront Karliah.
Go to the door as indicated on you map. Listen to it and the whispering lady will ask you to open the door. You need to get the key from the Jarl or the Court wizard. I strongly suggest pick pocketing one of them instead of . Once you have the key go back to the door and open it. The ebony blade will be there.