- Three cover kills
- Three ledge assassinations
Assistance Opportunity - Kill the Thugs
At the beginning of the memory Arno will be perched on top of a beam, and it would be wise to stay there until you plan your approach. Start by looking at the bridge below you, then further on to the small tunnel entrance to the left of that. That right there is your point of infiltration.
Drop down and make your way to the tunnel, then move through it until you climb up a ladder, continuing your ascension as you move up three flights of stairs. When you reach the top, use your Eagle Vision to spot two Extremists with their backs to you, then two more further ahead. Sneak up behind the closest two and use the Double Assassination to clear your way out the window.
At the ground level and out in the courtyard you'll see some thugs harassing some soldiers. To the east you'll also see a Sniper. You want to take him out first so he can't see what you're about to do below, and when he's down you'll need to systematically kill the thugs. It all sounds great on paper, but we fell to the ground and created quite a scene. After that we just murdered everybody and completed the objective anyway. As an alternative, once the Sniper is down you might want to consider using the Berserker Blade on one of the three Extremists. It's always fun to watch them kill each other.
Distraction Opportunity - Light the Fire
However that went down, when it's all over you're going to need to climb into a window on the west side of the courtyard. This should see you enter a room with bookshelves and a dead soldier, and you'll notice two Extremists roaming around outside. You could go with another Berserker Blade, but why not just sneak up and quietly take these two out? Just wait for their backs to be turned.
Unless you head back out the window there really isn't anywhere you can go except to the north or northwest, and you'll notice two more Extremists hanging out. One is taunting prisoners and the other is falling asleep. Wait for the guard to fall asleep, then snap into cover next to him and perform your first of three cover kills. After that, sneak up behind the Seeker and end his life.
Keep moving along until you come across a dining room, taking note of the two bad guys inside. One will be preoccupied with a door, and the other will patrol around the table. Get a sense for his patrol, then snap into cover along his route and score your second cover kill. With him down, sneak up behind his buddy and take him out silently. Now that the room is clear, make your way up the nearby stairs to the next level.
As soon as you hit the top of the stairs you'll find some soldiers fighting with Extremists. Help the soldiers out, then move forward into the next room and take cover behind the bundled up barrels. When the coast is clear, move through the iron gate and take cover behind the round concrete structure. Once more, wait for an opportunity, then sneak forward and take cover behind the bundled pallet next to where the Brute patrols. When he walks by, score your third kill from cover to complete the challenge, then take out his wandering buddy. You can ignore the two dudes messing with the window nearby. Well, ignore them until they are the only ones left alive, then use your Double Assassination to clear the room completely. You don't have to, but what's two more bodies?
Look for a gate on the west side of the room, interacting with it and picking the lock. If you find this difficult, try upgrading your lock picking skills in the Character Customization menu. When you're through, climb out the window and straight up the wall, hanging from it just before you reach the top. It's here that your Eagle Vision will show you two Snipers and a patrolling Extremist nearby.
Shimmy across the ledge and wait for the patrolling bad guy to look away, then use your attack button to perform your first of three ledge assassinations. Shuffle your way to the second Sniper, then score one more. When you're sure the final Extremist isn't looking, take him out quietly, then move back to where you were hanging from the ledge. Do not go after Rouille at this point.
Move to the south along the side of the wall until you reach a rooftop, then take note of the objective marker that is telling you to light a fire. Make your way there, setting the flag ablaze and completing your objective.
Drop back down to the wooden platform, then turn and look to the north. You should see your target at this point, as well as notice you are on the opposite side of the wall from where you got your first two ledge kills. As it turns out, you're still one shy of what you need, so attach yourself to the wall and move into position in front of the nearby Sniper. When the coast is clear, do your thing, then climb up and eliminate the Extremist that's patrolling nearby.
You've done well, assassin, but this is where you're going to make it or break it. The time has come to kill Rouille, and if you do this right you're going to earn Ninja Level 44 status (not a real thing).
Position yourself at the bottom of the stairs that lead to the platform, then toss a Smoke Bomb up there to disorient your target and his body guard. You should now be able to sneak right up the stairs and kill them both, also completing your objective.
Escape the Area
Just like every other assassination, you need to get clear of the crime scene. Jump over the closest wall you can find, then run until you are out of the shaded area and become anonymous.