No Full Synchronisation Requirement
Now it’s time for another Altair mission with the last of the Masyaf Keys. Slowly head out of the fortress (you don’t really have a choice given how old Altair is now!) with the Polos, and use the Apple to take out any attacking Mongols (press and hold the attack button to charge it up, then let go). Once you’ve passed the fortress gates, and then proceed down the hill towards the village. Keep using the Apple to clear groups, and you’ll eventually arrive at a tower. Climb the tower and use the Apple of Eden again to clear out almost every enemy in the area.
Descend the ladder and keep heading towards the square in Masyaf village with the Polos in tow. When you reach the bottom of the hill, a cutscene will play.
One thing to note is that the Memory is fairly strict in how far you can stray from your allies, and letting them get attacked will usually spell instant desynchronisation so try and keep a close eye on them!