The Hidden Blade Assassin's Creed in Depth

The goal is to poison the Pazzi conspirators of Sequence 5 and escape, without being seen at any time (no yellow bars).

Stefano da Bagnone
Despite appearances, this was the most difficult mission in this video to design. There are numerous groups of disguised guards patrolling in and around the courtyard, and you have to poison and escape so that nobody sees you. The trick comes down to careful timing. The guards in the courtyard start their patrols when they spawn. The target, on the other hand, starts his pattern of movement when you enter the courtyard (when you hear "Let us pray"). If you time your entry into the courtyard appropriately, the target will approach you just as the all of the patrols turn their backs. Poison him, and fast walk to the group of patrolling monks to re-blend, and then continue fast walking out of the courtyard. When you step out of the courtyard, turn left immediately to avoid a guard patrol that is headed your way from the right.

Bernardo Baroncelli
This mission is easy. Just blend with some civilians, and poison Bernardo when he approaches. Fast walk to get behind his bodyguards, and then you are free to make your escape.

Antonio Maffei
This mission is also easy, but I hate it because it takes so long. You have to climb up the tower and wait for a gap in the archers' patrol. Antonio also patrols around as he talks, and he uses the ladder during his rounds. Time your approach as shown, and you'll easily get past the archers to poison Antonio from behind. A leap of faith allows you to quickly and discretely escape.

Francesco Salviati
This clip was originally featured in the hyperblend exploit video:
http://www.thehiddenblade.com/hyperblend-exploit

The first jump from the horse to the wall is a little challenging. Ride slowly on the horse toward the grasping point next to the gate. As you approach the wall, tilt the camera down so that you can better gauge the distance between the horse and the wall. Keep holding the left stick up, and press the free hand button at the right time to dismount over the horse onto the wall.

The guards at the gate can sense that Ezio has breached their line. As a result, Ezio's status changes to Hidden (blue border around the mini-map) as he climbs over the gate. Nonetheless, he remains hyperblended and unseen during this time. If this partial detection bothers you, you can head back to San Gimignano and hire some courtesans. They'll follow you back to the compound, and you can use them to lure away the guard post. Another way is to hire the mercenaries to fight the guards, which technically keeps you from being detected, but it doesn't feel very stealthy.