Owar Stone is a crafting item, required for the item Great Warrior Stone, and all level 55 elite hats, level 55 elite armors, level 60 elite hats, and level 60 elite armors.
It is dropped by Guardian Beast (Warrior Road), Buldorados (Zhenmurshou Forest), Saigo, Nobunaga, Grand General Shinoda, and Shogun (Shogun Castle Floors 1-4).