Aerys II Targaryen, commonly referred to throughout the show as the Mad King, is one of the unseen characters in the Game of Thrones. He reigned as the king of the Seven Kingdoms up until the onset of Robert’s Rebellion. Aerys Targaryen died before the events of the series and was the last member to rule from the Iron Throne coming from House Targaryen.
Apparently, the rule of Aerys II Targaryen began benevolently. However, he later become unstable and ultimately deposed in a civil war by Robert Baratheon. Aerys II Targaryen was killed by one of his Kingsguards, Ser Jaime Lannister, who was later hailed as the Kingslayer.
Aery’s II Targaryen had only two children left- Viserys and Daenerys, they were taken to the Free Cities of Essos but determined to return to Westeros in order to reclaim what they consider their birthright. His ruling of the kingdom gradually grew erratic and full of murder. A final and fatal round of bloodshed came when his son Rhaegar kidnapped Lyanna Stark of Winterfell. This abduction made many houses rebel and oppose Aerys’ rule. The ordeal began when Brandon Stark protested the kidnapping of his sister and called for justice to prevail. In response, Aerys vouched for his arrest on grounds of treason and later made an offer to ransom him to his father. Surprisingly, when Rickard went to King’s Landing in order to ransom Brandon, the king had him arrested as well, thereafter; he executed both father and son.
This was the major root of the grand opposition as the noble houses of Stark, Tully, Arryn, and Baratheon facilitated the rebellion and destroyed the armies of the royalists in many engagements. This spilled over and led to the Battle of the Trident where Prince Rhaegar was killed. Thereafter, Aerys II Targaryen the king was betrayed by Lord Tywin Lannister, his former friend and the King’s Hand. Lord Twyin led an army meant to be defending the capital at King’s Landing but instead brutally sacked the city.
Angered by the betrayal, Aerys ordered his current Hand of the King, Wisdom Rossart, to conceal wildfire catches throughout Kings Landing. Worse yet, he took an oath that the capital be set on fire. According to him, the unbearable inferno would transmute Aerys into some kind of dragon, allowing him to prevail over his enemies. In a bid to bar King Aerys from burning the whole city and its close to half a million inhabitants, Ser Jaime Lannister decided to stab the King in the back and then cut his throat.
The death of the King ended the dynasty of Targaryen which up until then had ruled the kingdom from time immemorial. After his death, Aerys II Targaryen was succeeded on the Iron Throne by the rebel leader, Robert Baratheon. Despite the whole ordeal, the two youngest children of Aerys survived and were spirited away to the Free Cities.