After completing Loyalist mission, Samuel will drop you off at the Kingsparrow Island and after wishing you luck, he will ride off. From here you have two choices on how to enter the fort. You can either take the “Beachside Entrance” or the “Harbor-side Entrance”.
In this guide, we will take the Harbor-side entrance to get into the fort. Blink on to the stairs directly in front of you. Go up the stairs and you will see a large spotlight keeping sight on the area below. Blink on to the base of the spotlight to avoid detection from it.
When the spotlight turns its face to the right, dive into the water below and quickly blink onto the platform directly across the moving spotlight.
Turn to your right and jump down to get under the steel structure of platforms and stairs. Travel to the top left corner of this area. Use the rocks on the left to get back onto the top of the patform. When you skip over the railing directly in front of you, there would be a rat tunnel possess one of the rat nearby and go through it. You will come out on the other side of an active wall of light. Now you have gained access to the Kingsparrow fort.
Blink over the giant sealed gate in front of you. Take a few steps forward and to your left would be an open door with a sign over it reading “Life Boat Access.” Go to that door and while the two guards inside have their conversation blink to the left side of the hall, from there you can easily make your way across the length of the hall without being detected. Once across the hall, blink on to the steel platform above.
Quickly make your way to the courtyard again and wait there until the guard coming down the stairs from “Walkway Access” comes and turns back to go up the stairs again. Follow him and choke him out on the stairs. There will be one guard guarding the “Gatehouse Control Room.”
Take him out and then enter the control room. Inside the control room there will be a rat tunnel and a rat. Possess the rat, go through the tunnel, and you will emerge inside the Gatehouse. While you are still a rat get behind the solitary guard in this room so that you can take him out easily once you transform.
Take the “Elevator Key” hanging in this room and then head up the stairs. On your way to the top, you will meet two guards only. One reading a book and the other looking over the railing, take them out by getting behind and choking them out. This should be easy.
Once you get to the top, you will see that your path is blocked by an Arc Polygon and Overseers as well. However, to your left and right would be blue structures. There are pipes emerging from this structure that travels straight to the “Elevator Door.”
Get on to the pipe on your left via the structure. Travel its entire length and then finally blink on to the top of the elevator. Use the open hatch to fall into the elevator.
There are four guards ahead that guard the entrance into the light house. You can bypass the first easily as he is busy taking a leak. There will be two guards on the second floor. Wait for one of them to leave and then choke out the other when he turns his back towards you. Go up the stairs and you will find two guards. One of them will be on the top of the stairs with his back towards you while the other is further beyond.
Wait for the other guard to turn his eyes into any other direction and then take out the guard in front of you. Carry his body down before the other guard notices it. Come back and take out the final guard and progress inside the lighthouse.
Once inside, take the stairs to the top. You will locate Havelock madly rambling about the past with dead bodies of his tow allies around him. Sneak up behind him while he is talking to the air and finish him, if you want. The key to Emily’s cell is by the fireside though.
You need to quickly get it while the admiral is in some other corner of the room. Take the key and Emily’s cell is just beyond this hall to the left. Unlock the door to let Emily out and effectively end the last mission of the game.