Part of the Blue Cloth Set.

Where to Find the Warrior Greaves

The entire set can be purchased from a merchant in Liurnia of the Lakes. You’ll first need to have acquired an Academy Glinstone Key and gone through one of the seals that lead to the Academy of Raya Lucaria. Then, from the Academy Main Gate site of grace, ride southeast past the floating blue seal there and continue down the ramp to find the Isolated Merchant who sells these ashes.