Yann is a weaponsmith that is still young but already making a name for himself as someone able to make high quality blades. He has already learned a few trade secrets and early on in his career discovered an aptitude for metalwork, however most impact on his rise to fame has been that he is what some call a Savant with a magical master talent (See Magic of Aventuria pages 31-33)
This master talent (combined with his aptitude and exceptional skill) makes him quite effective to produce weapons (and metal armor) with improvements.
