Robin Arryn is a 6-year old boy who inherits the throne from his father after his sudden demise. Robin is played by Lino Facioli on the HBO series. His growth is stunted mainly due to his condition which causes frequent fits. He was born in King’s Landing with allegiance to House Arryn. His parents were Jon and Lisa Arryn. He is prone to histrionics especially when with his mother who praises her as a strong and rightful ruler of the realm. His mother makes no effort to school him on how to run the Vale. After Jon Arryn’s death, Lysa becomes skeptical. She becomes overprotective and takes Robin to the Eyrie, an impregnable fort in House Arryn to protect him. It is several thousand feet high with a single entry point which makes it hard to attack. It has sloped cells for housing prisoners with one side open to the air from which they risk rolling off in their sleep. The Eyrie has a high arch known as the Moon Door from where people are thrown off in an execution fashion. Lisa accuses House Lannister of poisoning her husband by writing to her sister.
When Catelyn Stark brings a prisoner Tyrion Lannister to the Eyrie whom she has accused of killing her son Bran, she is shocked to see Lysa still breastfeeding Robin despite his age. Tyrion is brought before the High Seat after agreeing to confess. He is offered a trial by combat where his champion and mercenary, Bronn, defeats Robin’s champion, and they are both set free. Robin is sad that Bronn has won since he wanted to ‘make him fly.’ Before leaving, Catelyn persuades Lysa to allow the Vale’s knights to fight alongside the Starks and Tully’s but she refuses claiming that they are supposed to protect her son Robin.
Robin is soon visited by his stepfather, Petyr Baelish, and cousin Sansa Stark. He is revealed to love the Moon Door especially after he demonstrates its purpose to his cousin, Sansa Stark by throwing off a crystal falcon given to him as a gift by Petyr. Robin soon finds Lysa building a snow castle in the courtyard and suggests they add a Moon Door to it. He knocks down one of the snow castle’s towers and an argument ensues. Lysa slaps him hard, and he runs off to the castle.
Her mother is later killed by Petyr Baelish (also known as ‘Littlefinger’ by throwing her off the Moon Door to her death. Peters rallies the two lords of the Vale; Lord Yohn Royce and Lady Anya Waynwood against the Lannisters. Robin is urged to go on an official visit of the kingdom lands but admits that he is too afraid to leave the Eyrie. He eventually departs on an official tour after some encouragement from Petyr. Petyr soon takes over as Lord Protector of the Vale.