Eldest son of Ser Stafford Lannister and Lady Myranda of House Lefford, raised at Casterly Rock as cousin to the queen and the Kingslayer. He won his spurs in his youth and grew into a great shaggy bear of a man, brown of beard and broad of shoulder, far better company than his father and a passable battle commander. He fought in the host Lord Tywin marched south against Robb Stark in 298 AC and survived the year that killed his father at Oxcross; afterwards, when Tywin returned to King's Landing, Daven took up his father's task and gathered a third western host at Lannisport, with a vow to shave neither beard nor head until Robb Stark's was on a spike.
After Tywin's murder in 300 AC, Queen Regent Cersei raised her cousin Daven to Warden of the West in place of Lord Kevan, who declined the appointment; she also sent him north to take up the siege at Riverrun that had stalled under his cousin Ryman Frey. Lord Tywin had betrothed him to a daughter of the Twins as part of the bargain that bought the Red Wedding, which Daven endured with good cheer, naming the prospect of his own Frey wife the one gift his late lord uncle had given him whose worth he could not yet measure. At Riverrun he yielded the supreme command to his cousin Ser Jaime when the latter arrived, and after Ser Brynden the Blackfish slipped the noose he set about the country with the rest of the western host, hunting outlaws across the riverlands.