While i was playing, in Memory Sequence 3 or 4 (It was quite early, i still hadn't gotten an entire set of the most basic Armour) and after completing a mission i got from promoting an assassin to be my last den master (it was one about a rich man paying merchants for the Templars, he claims he was corrupted by them) as soon as i completed the mission i suddenly got the Master Assassin Armour.
I am wondering, did i get this as a bug or did i get the Armour as a result of setting up my last Den Master
Best Answer
You are correct in your assumption.
The Master Assassin Armor set is obtained - exactly as you described - by giving every Assassin Den a Master Assassin.