The goal in this video is to kill all of the guards and Stefano da Bagnone without being spotted at all (no yellow bars), and without hiring mercenaries. (There's a neat trick to using mercenaries on this mission, which I will show in my next video.) This is a difficult mission to design due to the large number of guard patrols in a small area. I rely heavily on timed movements to avoid detection and careful placement of dead body distractions, which disrupt the guard patrols.
Here are the details:
0:20 Slow down as you near these guards. Otherwise, you'll be spotted when you make the first kill.
1:03 Keep right to avoid detection from guards inside the cloister.
1:07 Wait until the patrol is in front of the bench before killing them.
1:36 Two guards leave the cloister to inspect the dead body. Afterward, one of the guards will check the bench; the other will return inside to check another hiding place.
2:00 Leave another dead body in the same place. The remaining guard will come out to inspect the body and check the bench.
2:46 Check the GPS to see when the guard patrol is walking away from you along the inside wall (and therefore not facing you). Approach the entrance and leave the dead body for them to see the next time they come around.
3:20 Move this dead body for later use.
3:37 Enter the cloister to trigger Stefano and his companion to start their conversation and walk.
4:30 Stefano and his companion are outside. They won't move from this position.
4:52 Dump the body when you stand in the middle of the threshold.
5:04 Guards will inspect the dead body, and a guard will sometimes check the outside bench, which gives you a chance to kill him. If this does not occur, just keep trying. And trying. And trying.
5:28 Before each attempt, make sure that the guards have returned to their normal patrol before dumping another body.
7:25 This guard is twirling around (minor glitch).
10:06 The last 4 guards are difficult to remove by dead body distraction because they will tend to respawn while you aren't looking. Try to keep the camera pointed in their direction to prevent them from respawning.
10:11 Use throwing knives to kill them one at a time. Since you can't lock onto disguised guards, you will have to aim manually. Simply walk directly toward the guard you intend to kill. The throwing knife will fly in your last direction of travel. I find this to be the most reliable way of killing them all.
10:28 Hide in the haystack while they search for you. I've never been discovered in this hiding spot.
12:51 To kill Stefano and his companion, you'll need to carefully examine which way they are facing, which will vary on a case by case basis. If they are facing each other, you can use throwing knives from a distance to kill the companion. Sometimes, Stefano stays in the archway, so he can't see his companion. This gives you an opportunity to air assassinate the companion from the roof if you like.