Sword Art Online: Girls' Ops Vol. 7 (manga)

To steal the recipe for the Fairy Mallet and complete their quest, Silica and company infiltrate the Elves and Shoemaker guild. But Granze, the guild's leader, is not so easily outwitted--using the Gjallarhorn, a legendary instrument that summons a veritable army of soldiers to her side, she launches her assault! What's more, the soldiers are created from old SAO data, and their leader bears an uncanny resemblance to the Black Swordsman...