Checking out the official site, I ran across this tidbit of information:

European Lineage II players can now obtain the rare head accessory known as Sayha's White Mask. This stunning white mask adorned with a golden band is now available with the purchase of the Chronicle 5 box.

Follow these simple instructions to claim your exclusive item via PlayNC. Please note, this gift is available to all existing and future purchasers of the Chronicle 5: Oath of Blood box.