Pierre, Duke de La Vallière is the husband of Karin, and the father of Eleanor, Cattleya, and Louise. As a young man he went by the nickname Centurion, which means 'covered in ashes' in Helkeginian. Through an ancestor he is related to the royal family and thus a descendant of Brimir. In his youth he served in the royal army alongside fathers of Guiche and Malicorne, as well as his future wife. At some point he was made a Duke and given land in Tristain. Much like the relationship between his youngest daughter and Saito, the duo would often fight, with Karin using her wind magic to win the argument.
When the Duke first appears in the series he is shown complaining about Cardinal Mazarin and his support of the planned invasion of Albion. His disgruntlement comes from his belief that Tristain, despite receiving support from Germania, is still to weak to successfully challenge Albion. Due to this he refuses to support Louise's plan to join the military as he knows she will not survive. Later, he, his wife, and eldest daughter walk in on Louise and Saito kissing, an act that angers the Duke to such an extent that he orders for Louise to be locked in a tower for a year and for Saito to be beheaded. The duo manage to escape though and escape their punishment.
Shortly after his daughter and her fellow students return from rescuing Tabitha from Gallia, his wife decides to confront their daughter and deal with her as punishment for her treason. On hearing this, the Duke begins to grow nervous as he, more than anyone else, knows how powerful Karin is. While he attempts to calm her, his words fall of deaf ears as she proceeds to equip her old arsenal.
According to Louise Centurion Element is water. He is seen using many water spells in the Karin spinoff novels.