|The title of this article is conjecture based on information revealed in the A Song of Ice and Fire novels or related material and may be subject to change.
When Dalton Greyjoy and his Ironborn attacked the Westerlands, they were able to burn the Lannister fleet and sack Lannisport. There, they stole grain, gold and hundreds of women and girls, including Lord Jason's favorite mistress.
In the books
Lord Jason Lannister was the twin brother of Ser Tyland Lannister, and both vied for the hand of Rhaenyra Targaryen in their youth in 112 AC without successs. He fought for King Aegon II Targaryen and the Greens during the Dance of the Dragons, but was killed by Pate of Longleaf during the Battle at the Red Fork, leaving Casterly Rock in disarray and vulnerable to attack from Dalton Greyjoy and the Ironborn.