In the books
In the A Song of Ice and Fire novels, Lord Jason Mallister is a loyal bannerman of House Tully. He has at least one son, Patrek Mallister. As a young knight, he was defeated by Prince Rhaegar Targaryen in a tourney at Storm's End. During the early stage of Robert's Rebellion, he attended the wedding of Eddard Stark and Catelyn Tully, giving them lavish gifts. He participated in the Battle of the Trident, slaying three of Prince Rhaegar's bannermen, thus avenging the death of his kinsman Jeffory Mallister, who had been killed under orders of the Mad King.
Lord Jason takes part in the Tourney of the Hand and later, during the War of the Five Kings, takes part in the Battle of the Whispering Wood and the liberation of Riverrun at the Battle of the Camps. He returns to Seagard after Robb Stark is declared the King in the North.
Lord Jason is one of the seven nobles who are chosen to launch the funeral boat of Lord Hoster Tully. Jason meets King Robb on his march north to the Twins. Robb orders him to send two ships into the Neck, one carrying Galbart Glover and the other Maege Mormont, to find Greywater Watch.
In the fourth novel, Jason is forced to surrender Seagard to the Freys, since they threaten to kill his son Patrek, who was taken captive at the Red Wedding. Currently he and his son are imprisoned in Seagard.
|Lord:||Lord Jason Mallister||Heir:|
|Title(s):||Lord of Seagard|
|Current members:||Ser Denys Mallister|
|Deceased members:||Ser Jaremy Mallister|