This is the final main story quest in the game. It unlocks after completing the "Tainted Blood" quest - and to start it, you must return to the Observatory. Before that is possible, you will have to destroy two ships - a Man-o'-War and a frigate - blocking access to the bay.
Edward pursues his third of three primary targets: Laureano Torres.
The path you must follow is essentially identical to the one you took during your previous visit to Long Bay in "The Observatory" quest - only this time, you will traverse it after dark.
Upon reaching the beach where you previously parted ways with Adéwalé, you will encounter several Spanish soldiers. Kill the pair in front of you, then head through the bushes toward the tunnel entrance and kill two more soldiers. In both cases, the sleep dart method will work perfectly.
In the cave where the natives were during your first visit, there are now soldiers. Sneak up to the ones sitting by the campfire and wait until the patrolling soldier starts walking away. Just to be safe, you can shoot a sleep dart at the soldier standing near the edge, perform a double assassination on the two sitting by the fire, and then finish off the one at the edge. Retreat into the tall grass, wait for the patrolling soldier, and kill him as well.
Wait for the right moment when the soldier patrolling the area on the other side of the ravine is not looking in your direction, move forward, and hide in the tall grass. You can whistle to attract this soldier over to you and assassinate him.
Further ahead, you will encounter six more soldiers: two pairs, one standing alone, and one on patrol. It is best to take out the patrolling soldier first and then move between the rocks to the right, where the lone soldier is standing - lure him into the tall grass and kill him.
You can sneak past the first pair of soldiers by moving through the tall grass right next to them, creep up on the second pair from behind, and double-assassinate them both.
The rest of the path should be easy, with no more soldiers to eliminatem etc.
Simply enter the observatory through the same door - which will now be open - as during your first visit to this location.
Keep going until you reach the barrier of golden light and see a soldier who runs into it get disintegrated. Approach the barrier, wait for it to turn off, and then quickly cross to the other side. Do not delay, as the barrier will turn back on in a moment.
Climb onto the stone block in front of you and take out the two soldiers standing on it who will attack you. You can ignore the one lying on the ground.
Turn left. In front of you, you should see five adjacent stone segments moving up and down. Wait until the second segment from the right moves all the way down, then jump to it and grab hold of it.
When this segment moves all the way up, you should be at the same level as the small platform protruding from the middle segment. Once that happens, move onto this platform.
Wait for the sections to move again so that the platform you're standing on is above the platform protruding from the first section on the right. Then jump onto the platform protruding from the first section.
When this platform moves all the way up, jump from it onto the beam you can see on the right.
Make a few more jumps from one stone beam to the next, and after a while you'll drop down a little, which is fine, as you'll find yourself near the entrance to the observation room.
Several soldiers are waiting for you in the observatory room. You need to take them all out. Golden light walls periodically activate on the platform they are standing on, which you obviously need to avoid at all costs. However, there’s nothing stopping you from kicking your opponents so that they run into them.
Hint:
After eliminating all the enemies, head left and jump onto the platform with the first device. Once you do that, several stone blocks will extend, allowing you to jump across to the other side.
Hint:
You'll reach a stone wall covered in symbols, with golden light barriers appearing on it from time to time. You need to climb up the wall and make your way to the other side, avoiding contact with the barriers, of course. You won't be able to cover the entire distance during a single "off" cycle, so stop in places where you'll be safe. On the other side, you'll find the second of the devices you need to destroy.
Hint:
After destroying the second device, you'll be able to climb onto the platform where the last device generating the force field around Torres is located.
After destroying the last device, which will cause the barrier protecting Torres to disappear, simply approach the edge and perform an Air Assassination on him. And that's the end of the game's main story - get ready for a series of cutscenes and the end credits.
