As soon as he started the Oath was like, "Wait...... that's the Templar oath", then the Templar ring was pulled out and I started laughing and then said "Awesome", then Desmond said "Wait, what!?" and I laughed harder.
Stop your ignorance of Final Fantasy XI's awesome story. See it here. http://ffxicutscenes.blogspot.com/
I had it figured out after the opera scene never naming his order, the cordial discussion with his assassination target obviously implying they were old friends or allies. What makes for a better dramatic reveal a former Templar turned Assassin or vice versa?