House Swyft of Cornfield is a knightly house of the westerlands, sworn to House Lannister of Casterly Rock, though the Swyfts were once a full-fledged lordly line: a Lord Swyft fought and died for the greens at the Battle by the Lakeshore during the Dance of the Dragons. In the centuries since, Cornfield's lords were reduced to landed knights, though the old style "Lord of Cornfield" lingers in memory of better days. Their blue bantam rooster and the words "Awake! Awake!" are recorded only in semi-canon heraldry.
Ser Harys Swyft rises high in Tywin Lannister's service, his daughter Dorna's marriage to Ser Kevan Lannister binding Cornfield to the main Lannister line and making him grandfather to Lancel, Willem, and Martyn Lannister. Tyrion privately judges Harys a craven lickspittle, but Harys survives the Battle of the Blackwater, trapped beneath his dying horse until his man-at-arms Willit cuts him free, and goes on to serve as Cersei's Hand of the King and later master of coin during the crown's mounting debts to the Iron Bank.
His son and heir, Ser Steffon Swyft, marches with Jaime Lannister's relief force to Riverrun charged with guarding the baggage train, while the bantam badge is seen sewn on the breasts of broken men hanged for the sack of Saltpans, evidence that some Swyft men-at-arms turned outlaw amid the war's chaos.