Tataka said that your skills have improved and you should now improve your weapons as well. That is why you obtained the Essence of the Storm, Special Shulack Refiner and the Blessed Aurium Ingot and brought it all to the Jotun Studio together with Siel's Power Magic Weapon. The components were made into the crystal of Siel's Essence. When you brought Siel's Essence to Tataka, he created Siel's Dominant Magic Weapon.