Originally Posted by Neison

Is it worth doing each Raid boss for this Event, or should I be stashing fans for Raid boss Lvls 12+ or even just level 15? Since you get better rewards other than just headbands.

(I don't want to hi jack the thread with my question but it seems like a general thread for the current event.)

lv.8-11 bosses gives 1 upgrade mat. + 50% chance of another item (see list from Taon above).
lv.12-14 bosses gives 2 upgrade mat. + 50% chance of another item (see list from Taon above).
lv.15 bosses gives 3 upgrade mat. + 50% chance of another item (see list from Taon above).

you have to calculate or try, how many attacks you need for each lvl. to maximize your rewards.
e.g. if you need 2 attacks for a lvl 15, but only 1 for a lvl 14, then do only the lvl 14 boss.