This upgrade gives the mask, when worn, a 1 in 30 chance in combat that a wight ranger will spawn and fight for you. The mask cannot be used with Dreadnips and the wights will not appear in PvP. If you destroy the mask in its upgraded form, you can still reclaim it at the Statue of Death, but you will need to re-buy the upgraded from Moia for 10,000 coins, after the Dishonour among Thieves quest.