A daughter of House Westerling of the Crag, wed to Lord Jason Lannister, twin-eldest of the lions of Casterly Rock under King Viserys I. She bore him three daughters and a son, and was Lady of the Rock when the Dance of the Dragons broke out at the king's death; when her husband fell at the Red Fork in 130 AC and his host was shattered shortly after at the Lakeshore, she found herself widow-regent of the westerlands for her four-year-old son Loreon, with the iron lords of the Iron Islands tearing the western coast apart in her name.
Dalton Greyjoy, the Red Kraken, sacked Lannisport on her watch but could not take the Rock from her; with what remained of the Lannister fleet she went out herself and gave the ironborn battle at Kayce, breaking them on her own coast. She held the lordship until Loreon came of age and pressed her bid against the Greyjoys further yet, sending Ser Leo Costayne to invade the iron islands at the head of a Lannister army in the years after the Dance and seeing the Red Kraken's son Rodrik gelded and made her son's fool in revenge for her ravaged shore. Her death is unrecorded; she lived to see her Loreon grown into the lordship of the Rock and the westerlands restored.