The Shard of Farosh's Fang is an item from The Legend of Zelda: Breath of the Wild. It can be obtained from Farosh by hitting the dragon's mouth with an Arrow while it flies around either Lake Hylia, Lake Floria, or Gerudo Highlands.
Link can use Shard of Farosh's Fang as a material to upgrade certain Armor via Great Fairy. Link can also sell it to shops and merchants for 250 Rupees or to Kilton at the Fang and Bone for 110 Mon. It can also be used in Cooking as an additional ingredient to increase the chances of critical success boosting the effects of certain cooked food dishes or Elixirs.