Tracking down the arsonist who burned down Willis‘s workshop in White Orchard. There are a number of ways of completing this quest, but using Axii on the suspect is probably the best solution. Doing this quest is pretty much essential as it unlocks the dwarf as the first Armourer in the game.
Note that even though the game calls Willis a “blacksmith” during this quest he is actually an Armourer and cannot craft weapons. If you want a Blacksmith to craft weapons for you: go see the Quartermaster at the Nilfgaardian Garrison.
The Witcher 3 Guide 