The main purpose of Haedrig Eamon, the Blacksmith, is to craft armor and weapons for the player. He starts out at Level 1. Players can raise each crafter up to Level 12.
When I play in Adventure mode during a Season, I try and level up the Blacksmith as fast as I can (and I think other players do, too). Don’t forget to take a second to admire the artwork that changes each time you level up the Blacksmith. There are so many details to see!