After completing Lady Boyle’s Last Party mission, talk to Admiral Havelock and Overseer Martin. They’ll tell you to that it’s finally time to take down the Lord Regent. Visit Pierro to stock up, then Samuel the boatman to set off to Dunwall Tower. We are assuming that by this point you have access to the possession ability.
Sam will stop the boat near the gates so you’ll need to swim a bit. Head inside and you’ll see a platform in front of you. Use blink to get on top of it and blink some more to get even higher.
There are marks here on the wall which indicate the height and at the 60 mark, you’ll find yourself in an alcove. Right above you and further into the alcove is a small tunnel, as you walk along it, you’ll get to a part with two rotating wheels, and an opening blocked by iron bars.
Peek through the bars and Blink to two platforms a bit to the sides and move across the gap to a door on the other side.
Be careful while opening the door as there is an Arc Pylon on the other side. Use your blink ability to teleport behind a pillar to the left side of the room and drop down to the lower level. Here, you can take out the whale oil cell to disable the Pylon.
Once the Pylon is not a matter of concern, take the set of stairs in this room to the second floor and use the door to get outside. The first guard you see will probably have a ‘Dunwall side door’ key on him, so take it.
From here on forth, there will be a significant number of guards between you and the Dunwall Tower. Use Dark Vision to locate them through walls, take them down one by one and chuck them either into the ARC Pylon room or over the wall into the sea.
Follow the white marker and you’ll enter the same room with the large wheels but this time a floor above them. Proceed to the other side of the room and your path will be blocked by a Wall of Light.
To the left of it is a door that can be unlocked by the key you obtained before. Go through it and you’ll enter an area being patrolled by Tallboys and searchlights.
Go down the stairs and to the right of three arches. You need to move past these to the stairway on the other side. Use these and you’ll find yourself on the other side of the Wall of Light.
Continue onwards using Dark Vision and blink to avoid guards, Tallboys and searchlights, and you’ll soon find a courtyard with a large statue and a second wall of Light in it. You’re very close to the place where the Empress was killed.
Don’t bother venturing into the courtyard, instead blink to the top of the guardhouse to the right. Keep going forward while keeping the courtyard (and all its Tallboys and guards and Searchlights) to your left, and you’ll see a doorway with some lights above it. Use a series of blinks to get to it and quickly slip inside.
There is another door, which leads outside to the courtyard but this one leaves you a bit behind the Searchlights and Tallboys.
There is a crate to your right when you exit the doorway, jump atop it, then look at your left. You can see a guardhouse behind the second wall of Light that you can blink onto. Use this method to bypass the Wall of Light. Take care of the solitary guard you’ll find here and enter the tower.
Once inside, you’ll be in a large hall with another Wall of Light blocking your way. You need to make your way to the Lord Regent’s bedchambers (or panic room if you went through the last mission Chaotically).
When you enter the tower’s main hall, you’ll see a ledge which goes around the entire perimeter of the room above and to the right – blink onto it.
Use the ledge to get to the left side of the hall where you’ll find a room that contains some statues and two rats. Keep the door open, then possess one of the rats. Head back outside and enter a rat tunnel at the end of the hallway to bypass the Wall of Light.
You’ll end up in a dining hall. Use the door opposite to you and head to the door further to your right. In this corridor, there is a large pipe above that you can blink onto to avoid detection by the nearby guards.
Go to the end of the pipe and drop down near a door that leads to the torturers chambers. The only threat here is a dog and the torturer himself. Take care of them and pick up a nearby Purple Rune to trigger a cut scene with the Outsider.
After the cut scene, go back to the hallway with the pipe and at the end of it; you’ll find another door, which leads to the room opposite the dining room.
There are some guards here, but it’s not too difficult to take them out and bypass them. This room contains some stairs that you need to use. At the top of the flights of stairs you’ll find yet another Wall of Light.
You need to bypass this by taking the hallway to the right and then going left. There are guards patrolling this area that you need to take care of. There is a guard directly outside the Lord Regent’s bedroom, but we needn’t bother him.
Use the door to the right of the guard, take down another guard, and you’ll enter a room with a piano directly next to the bedchambers of the Lord Regent. These two rooms share one fireplace, which is important because you can use the opening to blink into the bedchambers and kill the Lord Regent.
Once he’s dead, open his safe with combination 9-3-5. Inside you’ll find an audio recording of his confession and a letter from the assassin demanding more money.
Note. You can simply steal this recording from Lord Regent’s safe and broadcast it to unlock political suicide achievement.
Go to the Broadcasting Station Samuel mentioned. Head back to the hallway outside the piano room and move to the other side of the Lord Regent’s bedchamber door (you’ll have to go through some guards) to find another door. This one leads to a hallway to a room with an Arc Pylon near some stairs.
You can bypass the Pylon by blinking right next to it. This way, you’ll automatically drop down the stairs and land right next to the Whale oil cell that powers it. Take it out and head back up the stairs to broadcasting station to find broadcasting officer.
The officer is a friendly NPC, and he will initiate a conversation with you. Ignore him and put the audio recording into the broadcasting machine. You are done with the mission so go back the way you came to get to reach Samuel to end the mission.