Gefeios said it is possible to improve your Noble Siel's Supreme Bow. So you obtained Vorpal Essence, Special Shulack Refiner, and Blessed Aurium Ingot, and you brought them to the Jotun Studio to make a crystal called the Essence of Siel. When you brought the Essence of Siel to Gefeios, he made you Siel's Dominant Bow.