Lysa Arryn

Lady Lysa Arryn is a recurring character in Game of Thrones. She is played by guest star Kate Dickie and debuts in the fifth episode of the first season.

Lysa Arryn is the widow of Lord Jon Arryn and the younger daughter of Lord Hoster Tully. She is the younger sister of Lady Catelyn Stark. She has a young son, Robin Arryn, who is the titular Lord of the Vale of Arryn. However, Lysa will rule as the Lady Regent of the Vale until Robin comes of age.

Season 1
After her husband Jon Arryn, the Hand of the King, dies, apparently of a fever, Lysa flees the capital and returns to the Eyrie, the seat of House Arryn, along with her son, Robin. She sends her sister Catelyn a letter claiming that the Lannisters murdered Jon Arryn for unknown reasons. This news convinces Catelyn's husband, Lord Eddard Stark, that he must accept King Robert's offer to become the new Hand so he may investigate further.

After apprehending Tyrion Lannister, Catelyn brings him to the Eyrie to be questioned. Lysa is furious with Catelyn for doing this. She and Robin hold Tyrion in contempt, ignoring his threats that his house will repay them for any harm they visit upon him. Lysa orders Tyrion given into the tender care of Mord, the castle jailer. Tyrion and Catelyn are both disturbed by Lysa's excessive coddling of Robin, including still breast-feeding him despite him being several years too old for it.

Tyrion convinces Lysa to give him a trial, only to protest his innocence. He demands the right of trial by battle, supported by the mercenary Bronn. Bronn wins the battle, killing Lysa's champion, Ser Vardis Egen. Tyrion and Bronn then depart the Eyrie.

Lysa receives a letter from King's Landing announcing that Eddard has been arrested for a traitor, but delays for a few hours before giving the letter to Catelyn, to Catelyn's annoyance. Catelyn asks that the knights of the Vale join the Tullys and the Starks in fighting the Lannisters, but Lysa refuses, insisting that the Vale knights must remain at home to defend Robin. Catelyn leaves, frustrated and annoyed.

In the books
In the Song of Ice and Fire novels Lysa is Catelyn's sister, who is distrustful of the Lannisters. She dotes on her son excessively. In the books her son's name is 'Robert Arryn', but this was changed for the TV series to avoid confusion with Robert Baratheon and Robb Stark.

Lysa married Lord Jon Arryn to tie three of the houses involved in Robert's Rebellion - the Starks, Tullys and Arryns - more closely together.