Assassin's Creed II Guide - Walkthrough
Sequence 8: Necessity, Mother of Invention
Memory 1: Birds of a Feather
Make your way to the memory start point in the San Marco district and stand in the marker to begin. You must follow the two Templars to eavesdrop on their conversation. Don't follow too closely, though, as doing so will make them suspicious. If the arrow above either of the targets' heads begins to fill with yellow, back up immediately to avoid being detected.
Tail the Templars to eavesdrop on their conversation.
At one point you'll come to a short bridge blocked by guards. The Templars are able to pass through without any trouble, but the guards certainly won't let you pass. Hire the nearby group of Courtesans and use them to distract the guards while you slip past. Continue following the Templars and you will eventually come to an archway blocked by guards. Hire one of the groups of Thieves nearby and order them to lure the guards away so you can continue following the targets.
Follow the Templars until they reach the Ponte Di Rialto, at which point a cutscene will close the memory.
Memory 2: If at First You Don't Succeed...
Speak to Rosa at the Palazzo Della Seta to start this memory. Make your way to the green target on the Mini-Map with Antonio. You must find some way into the Palazzo Ducale Di Venezia. Scout the area with Antonio by heading to the markers that appear on the Mini-Map. Wait for Antonio to stand in each marker to trigger a cutscene. Straying too far from Antonio will desynchronize the memory, so stop and wait for him to catch up if necessary.
After the third marker, follow the scaffolding up to the roof of the basilica, using the barrels covered by white cloth as a starting point.
Memory 3: Nothing Ventured, Nothing Gained
Visit Leonardo at his workshop in Venice to begin this memory. It's a short one; just crash the flying machine on any rooftop to complete the memory.
Crash the flying machine to complete the memory.
Memory 4: Well Begun is Half Done
You must clear the guards in the four areas marked by red targets on the map. Simply travel to each red target and kill all of the marked guards in the area. There are two Brutes at two of the four areas; they're close enough to each other for Ezio to perform a double assassination with the Hidden Blades.
Clear the four areas of guards to complete the memory.
Memory 5: Infrequent Flier
Make your way to the mission start point on the rooftops and stand in the marker there to start the memory. You need to get on top of Palazzo Ducale using the flying machine and then assassinate Carlo Grimaldi.
Da Vinci's flying machine is quite easy to control: push the Left Stick up to dive, and the Left Stick down to rise. The tricky part comes with the need to keep the craft in the air using the fires Antonio's men have strategically set around the city.
Kick a guard while using the flying machine to unlock the “Fly Swatter” achievement or trophy.
You'll also want to unlock the “Fly Swatter” achievement or trophy during this memory by kicking an archer while using the flying machine. At the time of writing, you won't be able to replay this memory unless you start a new game, so this is your only chance to earn this achievement/trophy on your current playthrough.
You can nab this achievement/trophy early on in the flight. Start by flying over to the first two fires, but ignore the third in line and instead continue east to the four archers on the rooftop of the building there. To kick an archer you have to be flying low enough and locked on to a target using the LT/L2 button. If you're locked on to an archer and Ezio is flying low enough, he will automatically kick the archer when he reaches him. Once you have the achievement, pull up immediately by pushing the Left Stick down to avoid crashing. Even if you do crash, at least you'll have the achievement/trophy and won't have to go for it again during the next flight.
Continue following the fires northeast. Dive down as you reach the next fire and after flying over it, rise up by pushing down on the Left Stick to gain more height. Archers will fire at you from the rooftops, but their arrows are easy enough to avoid and the flying machine can take a decent amount of damage (the condition of the craft is indicated below Ezio's health and social status in the top-left corner of the screen).
Follow the fires until you're near Palazzo Ducale, at which point direct the craft toward the marker on the rooftop.
Using da Vinci's flying machine to land on top of Palazzo Ducale
Once on top of the palazzo, you must make it to the marker by the stairs at the north end without being detected. Stand on top of the wall by the fence and leap toward the awning next to the marker, pressing the B/Circle button to Grab hold of it as you're falling. There's a guard patrolling along the stairs, but he shouldn't have enough time to detect you if you hit the maker immediately after landing.
After the cutscene, equip your Hidden Blade, climb through the window at the south end of the room, hop onto the stairs railing and pounce on Carlo Grimaldi. All that's left to do is escape. Sprint right through the front door at the south end of the courtyard and lose the guards to complete the memory and Sequence 8.
Assassinating Carlo Grimaldi