Fortress Ballista is a Legendary Hand Crossbow for the Demon Hunter in Diablo III, added in patch 2.4.0. It requires character level 70 to drop. The unique affix effect stacks and renews with each application: the potency is added to the remaining one, and then duration refreshes. Any attack suffices regardless of Proc Coefficient and number of enemies hit. Ashnagarr's Blood Bracer does not affect this shield.