Note: If you’ve already drived the Jarl out of Whiterun due to the CIVIL WAR quests (like I did), you can still do this quest! The Jarl is just located in the Blue Palace in Solitude now…

Go find Jarl Balgruuf wherever he is and ask him about his children. He will tell you about his oldest son Nelkir, who is trouble, and will ask you to speak with him. This starts the quest “The Whispering Door” properly.

Go find Nelkir at Dragonsreach, who will claim he knows a lot of things his father doesn’t know he knows. Ask him how, and he’ll eventually tell you about the whispering lady. I guess we’ll just have to see this for ourselves! Go to the basement and find the door the quest marker points to. Now interact with it. Holy shit, the door talks! Well, whispers. The door will introduce itself as Mephala, the Lady of Whispers. She will state that she’s been waiting for you and asks you to open the door. Go back and talk to Nelkir again, who will tell you that only two people have the key to the door: his father and Farengar, the court wizard. He also mentions that no one would notice if Farengar went missing! Well, assassination is a little overkill, just save your game and pickpocket the key off of one of those two marks…

With the key in hand, go open the whispering door. Inside you’ll find a book warning you against taking the Ebony Blade, but take it anyways. Mephala will congratulate you, but will tell you that the Ebony Blade is WEAK right now, and in order for it to be strengthened you must use it to KILL those who are closest to you (companions, followers, friends, etc), which is a tough choice to make. Regardless, the door’s secrets are unraveled and this quest has come to an end.