|Find the source of power in Silverdrift lair|
This quest can be given to you at any time in the game. A courier will run up to you and give you a "Message from a friend" which will say:
you caused a bit of stir in [Random Area] when you demonstrated the power of your Thu'um. Not everyone is anxious for the return of the Dragonborn. I for one desire to see you grow and develope your talents. Skyrim needs a true hero these days you should turn your attention to Silverdrift Lair. I understand it holds a mysterious source of power that can only be unlocked by a dragonborn.