Full Synchronisation Requirement - If attacked, kill five guards in close combat without getting hit
You begin the Memory at Sofia’s bookshop, the old Polo trading post. Search the rooms until you find the body of a fallen comrade. After the scene, you’ll begin outside of a familiar gate, on a rooftop, with what seems like legions of assassins at your disposal. However, if you want to get the full synchronisation objective, you’re going to have to forgo use of your apprentices in favour of some good old fashioned close combat.
Jump down, and run past everyone through the gate. You should very quickly run into a large group of guards, with reinforcements closing in. Draw your dagger, as it’s a considerably faster weapon for counter kills and execution streaking, and get stuck in. Try and get a 5 kill streak off before reinforcements arrive, or else you’re going to have to try extra hard to get a large enough group of guards together without your assassins ‘helping’ you take care of them. After you’re done with the side objective, feel free to use/abuse the unlimited signals and arrow storms you have access to for this Memory to take reaching the goal a little quicker and easier.
Once you reach the goal (with a trail of dead Templars behind you, of course) you’ll get a cutscene and another twist. When the Memory ends, use fast travel to head to the next one (you’ll want to keep going!).