Aerys II Targaryen

Aerys II Targaryen, popularly called the Mad King, is an unseen character in Game of Thrones. He is deceased when the events of the series begin. Liam Burke was cast to play him in flashback in Season 1, but the scene was cut for time and pacing. Aerys Targaryen was the last member of House Targaryen to rule from the Iron Throne. He was famously mad and was deposed by Robert Baratheon in a civil war.

Background
Aerys Targaryen, the Second of His Name, was a King of Westeros and the last member of House Targaryen to sit the Iron Throne. Nicknamed the Mad King, his reign became increasingly erratic and murderous. A final round of blood-letting, unleashed when his son Prince Rhaegar kidnapped Lyanna Stark of Winterfell, saw the Seven Kingdoms rebel against his rule. Brandon Stark protested the abduction of his sister and demanded justice. Aerys had him arrested for treason and then offered to ransom him to his father Rickard Stark. Aerys summoned Rickard to court and when he arrived publicly executed both father and son.

The noble houses Stark, Tully, Arryn and Baratheon raised the flags of rebellion and destroyed the royalist armies in several major engagements, culminating in the Battle of the Trident where Prince Rhaegar fell. King Aerys was betrayed by his former friend and King's Hand, Lord Tywin Lannister, who led an army to apparently defend the capital at King's Landing but then brutally sacked the city instead. Aerys was killed by a member of his own Kingsguard, Ser Jaime Lannister.

Aerys was survived by his two youngest children, Viserys and Daenerys, who fled to the Free Cities.

Season 1
Aerys ordered Ser Barristan Selmy of the Kingsguard to destroy the Kingswood Brotherhood. Selmy himself killed their leader Simon Toyne.

When Lyanna Stark was kidnapped by Prince Rhaegar Targaryen, her brother Brandon rode to King's Landing seeking justice. Aerys imprisoned Brandon and ordered that his father Rickard Stark ride south to answer for his son's impertinence. Against advice, Rickard agreed, assuming that the matter would be settled through a trial or a bargain of some kind. Instead, Aerys had Lord Rickard burned alive whilst Brandon watched, and then had Brandon strangled.

The new Lord of Winterfell, Eddard Stark, declared war against Aerys, supported by Lyanna's betrothed, Robert Baratheon, and the powerful lords Hoster Tully and Jon Arryn. This sparked the beginning of the war known as Robert's Rebellion, which led to the near-destruction of House Targaryen and its removal from the Iron Throne. Rhaegar was killed by Robert at the Battle of the Trident.

Sandor Clegane tells Sansa Stark that Aerys had Ser Ilyn Payne's tongue torn out. Jaime Lannister is confronted by both Eddard Stark and Robert Baratheon about killing Aerys. Jaime killed Aerys after he ordered King's Landing burned during Robert's Rebellion. His final words were "Burn them all." His death occurred during the Sack of King's Landing. Eddard mentions that Grand Maester Pycelle served King Aerys.

Maester Aemon reveals that he is the uncle of King Aerys and because of his oath to the Night's Watch could not interfere during the rebellion.

Season 2
Wisdom Hallyne of the Alchemists' Guild mentions Aerys as a fervent supporter of the guild. He warns Bronn that he would not have dared to insult the guild while Aerys was alive.

In the books
In the Song of Ice and Fire novels, Aerys II's reign began with great promise. Taking the throne at only the age of 20, Aerys installed a number of younger, vigorous and capable men in positions of power, whilst his own son Rhaegar showed promise of being a great king in his turn. However, Aerys, who occasionally showed signs of a terrible temper, became erratic following the brief uprising known as the Defiance of Duskendale, when he was held prisoner for several months by a rebellious lord. Aerys's fury on that occasion was terrible: all of those involved in the incident were killed, several by being burned alive. After that, his rage could no longer be held in check. After he burned several prominent lords alive and sanctioned his son's kidnap of Lyanna Stark, several noble houses rebelled against him.

In a minor change from the books, Aerys II is said to be the son of King Aegon V Targaryen, rather than his grandson. His father, Jaehaerys II, appears to have been eliminated from the roll of kings. The reason for this appears to be to simplify the relationship between Maester Aemon - Aegon V's older brother - and the other Targaryens (by making Aemon Daenerys' grand-uncle, rather than great-grand-uncle).

According to comments made by author George R. R. Martin, the TV series actually already cast an actor to play Aerys II during Season 1, presumably for flashback scenes, but ultimately no flashbacks were used in Season 1. According to casting company information, Liam Burke was cast to play him in the Season 1 flashbacks,, but it is unknown if he will ultimately be the same actor used if Aerys II does appear in flashbacks in later seasons.