"Do you really wish to know?" — Spoilers from the books and/or adaptations to follow!
Fergus Graem is a dwarven journeyman Armorer working in Crow's Perch, central fortress of Velen (in Kingdom of Temeria). He shares a work area with Yoana, a true master of work.
He's considered by all his colleagues the best armorer in Velen. This story is not actually true: To run Fergus' forge is in fact Yoana, his assistant.