Jon Arryn

"Jon Arryn is dead."

- Catelyn Stark

Jon Arryn is a minor character in the first season. He is played by guest star Sir John Standing and only appears in the series premiere. The character is deceased when the series begins. He was the Lord of the Eyrie, Warden of the East, Defender of the Vale, and Hand of the King to Robert Baratheon.

Background
Jon Arryn was the Lord of the Eyrie and the head of House Arryn, one of the Great Houses of Westeros. Jon was the Warden of the East and Defender of the Vale. He was a respected nobleman and both Eddard Stark and Robert Baratheon fostered with him. The Mad King condoned the kidnap of Eddard's sister and Robert's betrothed Lyanna Stark. The Mad King had Eddard's father and brother killed for protesting against the kidnapping. When he then demanded that Eddard be turned over to the King's justice, Lord Arryn rebelled, calling his banners to war. House Stark and House Baratheon followed suit. The rebels forged an alliance with House Tully through marriage, with Eddard married to Catelyn Tully and the then-elderly Jon to the young Lysa Tully.

After the rebel victory in the war, Robert became King and appointed Jon as his Hand. Jon served the realm well for many years as Hand of the King. Indeed, Jon Arryn was essentially the man really holding the realm together for the next seventeen years, while Robert drank and ate and held expensive tournaments.

Jon Arryn died in King's Landing immediately prior to the events of the series, sparking King Robert's search for a replacement. Jon is survived by his wife Lysa and their six-year-old son, Robin Arryn. Jon was investigating the legitimacy of the children of Queen Cersei Lannister when he died. He found that they were not Robert's offspring by comparing their appearance to Robert's bastards based on the genetic preponderance for dark hair in House Baratheon.

Season 1
Jon Arryn's body is laid out in state in the throne room of the Red Keep in King's Landing. Ser Jaime Lannister and Queen Cersei discuss Jon's attempts to learn the truth about their incestuous relationship and his failure to do so. Later, news of Jon's death reaches Eddard Stark at Winterfell, who is shocked and upset as he considered Jon to be a second father to him.

When Eddard Stark attends his first Small Council meeting in King's Landing, he is shocked to learn that the realm is six million Gold Dragons in debt, and refuses to believe that Jon Arryn would let this happen. Grand Maester Pycelle and Renly Baratheon explain to Lord Stark that while Jon gave wise and prudent advice, King Robert did not always follow it.

It is revealed to Eddard Stark that Jon Arryn was tracking King Robert Baratheon's illegitimate children, for unknown reasons. Varys privately warns Eddard that he thinks Jon Arryn was murdered by an unknown party for asking too many questions, using a rare and untraceable poison known as the Tears of Lys

Season 2
Under forceful interrogation by Tyrion Lannister, Grand Maester Pycelle confesses that he knew that Jon Arryn had discovered the truth about Queen Cersei's children. From discovering Robert's illegitimate children, such as Gendry, Jon realized that none of Cersei's children were Robert's, but bastards of incest fathered by Jaime Lannister. Pycelle states that Jon Arryn intended to act and reveal his discoverings to King Robert. When Tyrion accuses Pycelle of having Jon poisoned to keep the truth from getting out, he angrily denies that he killed him. Tyrion then points out that Pycelle must have realized that someone had poisoned Arryn and he wasn't simply sick, but he let him succumb anyway, so he has Pycelle thrown into the dungeon.

Behind the scenes
Originally it was intended that Jon Arryn's death in King's Landing would open the series, following the depiction of the book's prologue, and the event would be discussed by Grand Maester Pycelle and Queen Cersei Lannister in a new scene not in the books. In the end this scene was not filmed for the pilot episode in favor of maintaining the opening from the novel. Jon Arryn was played in these scenes by John Standing, though it is unknown if the actor will be retained for flashbacks later in the series, or even if Jon Arryn will ever actually appear in flashback scenes.

In the books
In the A Song of Ice and Fire novels, Jon Arryn is a great lord, wise counselor, and canny tactician. He is loved as a second father by both Eddard and Robert, and commanded great respect in the Vale of Arryn. His nephew and heir Elbert Arryn was among Brandon Stark's companions who were imprisoned and killed by the Mad King, sparking Jon Arryn's decision to join the rebellion.

In the books, Eddard Stark discovered that Arryn and Stannis Baratheon inquired together about Cersei's children and Robert's bastards. In fact it was Stannis who initiated the investigation, while in the TV series he is not mentioned at all in respect of Arryn's actions prior to his death.