Evil Crystals

Evil Crytals are a small obtainable treasure in Skyward Sword. They are usually dropped by Cursed Bokoblin, Dark Lizalfos, and Dark Keese. They can also be found in random treasure chests scattered across the land. Very rarely, they can be dropped by Gossip Stones after summoning them with the Harp. Link bring this treasure to the Scrap Shop in the Bazaar in order to upgrade his equipment. They can be used to upgrade the Bow and Bug Net. It's one of a few uncommon treasures in the game.