Hail Sithis! (quest)

Walkthrough
After failing to assassinate the real Emperor, and witnessing the destruction of the Dark Brotherhood Sanctuary, and most of the members, it is time to finish the job.

Talk to Nazir
Talk to Nazir about your next plan of action: obtaining the location of the true Emperor Titus Mede II from Amaund Motierre.

Talk to Amaund Motierre
Motierre will be at the Bannered Mare in Whiterun from now on. Talk to Motierre and tell him that the contract is still valid. He will reveal the location of the true Emperor: on a ship off of Solitude's docks called the Katariah (marked on map).

Board the Katariah
The Dragonborn will have to swim to the ship, and climb up the anchor chain at the north-east side. On board of the Katariah fight your way past sailors and Penitus Oculatus to the Emperor's room.

Note: It is possible to stealthily sneak past all guards and also loot all chests. Use invisibility potions for the more tricky areas.

Kill the Emperor!
Kill the Emperor. He puts up no fight, and gives you another bonus objective: kill the man who initiated the contract.

The Emperor is a rather fine and educated man, really a pity he needs to die.

(Optional) Kill Commander Maro
There is the optional objective of killing Commander Maro. He has decent gear, and the satisfaction of his death is the main reward.

Report to Amaund Motierre
Report back to Motierre to learn the location of your final payment: an urn inside the original meeting area of Volunruud.

Retrieve the payment
The urn contains 20,000.

(Optional) Kill Amaund Motierre
Optionally, fulfil the Emperor's dying request by killing Motierre.

Tip: Close the door of Motierre's room at the inn, move to the far corner, use a bow and arrow, a steal kill should then be possible.

Motierre should have another few gems on his body.

Report to Nazir
When returning to the Dawnstar Sanctuary, interestingly now followers can enter as well, Nazir will congratulate the Dragonborn to a job well done. The Dragonborn can choose to lie about the actually reward amount, but that is of no consequence.

Nazir points out that the money could be used to repair and upgrade the Sanctuary, by talking to Delvin Mallory of the Thieves Guild in Where You Hang Your Enemy's Head….

Hail Sithis! (Aufgabe)