The Silence Has Been Broken

Speak with Astrid
After having completed one or both contracts for Nazir, Astrid decides that the Dragonborn should in fact go to Volunruud as the Night Mother suggested, and to meet with Amaund Motierre there.

Before leaving the Dark Brotherhood Sanctuary the Dragonborn can talk to all the members about the subject.

Speak with Amaund Motierre
Once at Volunruud the Dragonborn speaks with Amaund Motierre who reveals that the contract he is offering the Brotherhood is to assassinate the Emperor. For this, he gives the Dragonborn a Jeweled Amulet (as advance payment) and a sealed letter addressed to Astrid.

The Dragonborn should (optionally) use the opportunity to grill Amaund some more about the motives behind the contract.

Talk to Rexus
The Dragonborn can then speak with Rexus, Motierre's bodyguard. (This is pretty pointless.)

Deliver the letter and amulet to Astrid
Return to Astrid at the Sanctuary where she will instruct the Dragonborn to bring the amulet to an aquaintance named Delvin Mallory at the Thieves' Guild in Riften to have the amulet appraised.

Note: Should the Dragonbron already be a member of the Thieves' Guild, possibly even the Guild Master, Delvin will comment on the fact that the Dragonborn sure likes to take on all sorts of "challenges".

Show the amulet to Delvin Mallory
Delvin Mallory at the Ragged Flagon reveals that the amulet is indeed valuable and very rare. It is usually only given to members of the Elder Council. When asked if he will buy it, he agrees and gives the Dragonborn a Letter of Credit over 15,000.

Report back to Astrid
The Dragonborn returns to the Sanctuary and gives Astrid the letter.

And so the plan to assassinate the Emperor begins. Astrid gives the Dragonborn the details of the next mission: to kill the Emperor's cousin, Vittoria Vici, at her own wedding.

Jenseits der Stille