The Weapon Master is the official who trains the guards of Spielburg, and, presumeably, participates Spielburg's castle defense should the occasion arises.
He trained the Baronet, who didn't heed close instruction and was too impatient to learn all that he could. He refused to train young Elsa by reason of her being a 'mere' girl, though he admitted that she had natural talent and played close attention.
He's an arrogant man, but his skills are the real deal, and for a gold coin he'll have a sparring match with a Fighter and give some pointers upon the hero's most-probable defeat, and he'll be civil and respectful enough while this process is ongoing.
Should the hero actually best him, the Weapon Master declares he's going to retire after being beaten by a such a clumsy lout, he'll wish all kinds of misfortune on the hero, and he will not be seen again. The hero must be as strong as he can be in pretty much all his combat stats, and get his timing for blocking and attacking correct, making the Weapon Master the greatest challenge for a Fighter in Spielburg.