Jervis was the Armsmaster at Forst Reach. He served as a mercenary with Withen Ashkevron. When Withen inherited his position as Lord of Forst Reach, he brought Jervis with him, installing him as Armsmaster. It is implied that Withen felt he owed Jervis for watching his back, perhaps even saving his life.
Jervis was not qualified to be an armsmaster. He only knew one style and didn't teach even it well. He muddled through until Vanyel was old enough to begin weapons training. Withen suspected Vanyel might be homosexual, and didn't approve. He wanted Jervis to cure him, up to and including beating it out of him. At the same time, Vanyel, who was completely unsuited to Jervis' one weapons style, rebelled. He dodged practices and did as little as possible when he was forced to attend. Jervis worried that as they lived on the border, there would someday be a fight, and an ill-prepared Vanyel would be sent out to fight and die. He was plagued with nightmares of this scenario.
The stress and anxiety all burst out in the fit of temper when Jervis broke Vanyel's arm on the practice field. It might have been even worse if Lissa hadn't been alerted and stopped him. Jervis wrestled with what had happened for many years before making peace with himself. While they worked together to sort out the mess of Tashir and the murdered royal family of Lineas, Jervis made peace with Vanyel too. He even saved Vanyel's life, dragging him through a Gate back to Forst Reach, pulling him out of the collapsing Linean palace.
After the Lineas-Baires Annexation was negotiated by Vanyel from his bedside where he was recovering from his injuries, Vanyel named Jervis Fifth Councilor and Marshal for the new March of Lineas-Baires. Jervis resettled in Highjorune with the rest of Lord-Baron Tashir's staff. He eventually married Melenna, who had been named Tashir's castelaine.