Those who can't see the image from work:
Double AP
Extra black buillon whenever you earn BB, you earn one extra
+50% Aureus of Initiation (from Scenarios)
+50% White Marks of Venice (from PvP)
+50% AEGIS Research
Big recruiting bonuses
Unlike other games where double xp or whatever almost ruins the game as it forces progression beyond your 'level' as you devour content, basically, you never have enough ap, bb, aureus, marks, or research (well, you can have enough research, but if you're in kaidan, you are probably lacking in sequins anyway)
There is a bag. It contains cool things.
Also, here is the link from the event from last here. Most of the details should still be accurate:
http://www.tswdb.com/events/anniversary-events-of-2015/
