House Jast is a noble house of the westerlands. According to semi-canon sources their banner is an inverted pall between three lion's heads, yellow on black.
House Jast was formed by the union of First Men and Andal nobles during the Andal invasion.
During the misrule of Lord Tytos Lannister, Lords Jast and Falwell became embroiled in a private quarrel. Rather than seek a ruling from Casterly Rock, the lords decided to settle the matter with a melee. Nine men were killed, twenty-seven maimed and wounded, and still the quarrel raged on.
Antario is freed at the end of the war. The wounds received and the time he had spent prisoner affect him greatly, leaving him a shadow of the man he had been. Lord Jast joins the group which escorts Lord Tywin Lannister's body from King's Landing back to Casterly Rock. Ser Jaime Lannister sees him armored in black steel, with three gold lion's heads on his breastplate.