|Title|| Lord of Casterly Rock|
Warden of the West
Lord of the Westerlands
|Allegiance|| House Lannister|
|Died||In 130 AC, at Battle at the Red Fork|
|Spouse||Lady Johanna Lannister|
|Book(s)|| The Rogue Prince (mentioned)|
The Princess and the Queen (mentioned)
The World of Ice and Fire (mentioned)
- For the father-in-law of Tywin Lannister, see Jason Lannister (son of Gerold).
During the civil war known as the Dance of the Dragons (129 AC-131 AC) Jason was loyal to King Aegon II and the greens against Rhaenyra's claim, while Tyland was Aegon's master of coin.Jason was killed by Pate of Longleaf in the Battle at the Red Fork, however, which left Casterly Rock in considerable disarray. Jason's widow, Lady Johanna Lannister, defended the westerlands from the Red Kraken, Lord Dalton Greyjoy.