Aegon's conquest of Westeros may spawn another Game of Thrones prequel, as it is one of the most important events in Westerosi history. Before he united most of Westeros into one realm, the continent was divided into six kingdoms and one principality. Aegon the Conqueror landed at the mouth of Blackwater Rush with two sister-wives and their three dragons. He seized power and established the ruling Targaryen dynasty of Westeros, and he was the first king on the Iron Throne. Since Aegon had entered into polygamous marriages (with his sisters), a major rift in the family appeared when Maegor usurped the throne of his half-brother, Aenys's children.
Aegon fathered two sons, one from each sister-wife. While Aenys from Rhaenys was his eldest and thus heir to the throne, Maegor from Visenya was his youngest. Aenys was the second king to sit the Iron Throne and Maegor I was the third. From the time of Maegor I to the last Targaryen king, Aerys II aka the Mad King, the history of the Seven Kingdoms is filled with conspiracies, conflicts, and most notably, the war of succession which is the focal point of HBO's ongoing Game of Thrones prequel. The realm saw a much more tumultuous time after Viserys I's reign ended. His son from Alicent Hightower, usurped his half-sister, Rhaenyra's throne, thereby marking the beginning of the civil war known as the Dance of the Dragons. The Targaryens were eventually displaced from power in Robert's Rebellion and House Baratheon won the throne. Later, the Seven Kingdoms were at war with one another during the War of the Five Kings. As such, in the bloody history of the realm, several monarchs hold the record for the shortest reigns on the throne.
Aenys I - Five Years
King Aegon I Targaryen's heir, Aenys was at Highgarden when he died of a stroke in 37 AC. He mounted Quicksilver and flew to Dragonstone for his father's funeral. Hailed as king, Aenys gifted his half-brother Blackfyre, asking him to wield the sword in his service.
While there exist conflicting reports about his coronation, Aenys nonetheless was the second Targaryen king on the Iron Throne. His reign ended after the Faith Militant rose against him for tactlessly marrying his eldest daughter, Princess Rhaena to his son, Prince Aegon. The Faith denounced this marriage and expelled Septon Murmison for officiating it. When the Faith could no longer turn a blind eye to what they essentially saw as a vile sin, an uprising began. Aenys fled to Dragonstone and died in 42 AC, after only ruling for five years. He was neither decisive nor a capable warrior like his father. He lacked the diplomatic skills to negotiate Targaryen marriages with the Faith and failed to quell the Faith Militant uprising.
Rhaenyra Targaryen - The Half-Year Queen
Viserys' firstborn daughter and heir, Rhaenyra Targaryen was crowned on Dragonstone by her husband and uncle, Daemon Targaryen in House of the Dragon season 1, episode 10, "The Black Queen." Following this, hostilities broke out, and the realm plunged into a bloody civil war. Rhaenyra's secondborn son, Lucerys Velaryon became the first casualty of the Dance. A defenseless King's Landing fell to her in 130 AC when Aemond Targaryen and Criston Cole of the Greens marched on Harrenhal. Daemon and Rhaenyra flew over the capital city while the Sea Snake - Corlys Velaryon's fleet arrived to the east of Blackwater Bay. The city fell in less than a day's time and Alicent Hightower was forced to surrender.
While Aegon II escaped, his grandfather, Otto Hightower was executed. Alicent Hightower and Helaena were held captive, with the former proposing the Seven Kingdoms be divided between the two factions, Rhaenyra rejected them. More executions followed and Rhaenyra's paranoia grew. After her half-sister, Helaena died by suicide, the small folk rose in revolt against her. Rhaenyra fled King's and once she reached Dragonstone, she was betrayed by Ser Alfred Broome. In the end, Aegon II fed her to his dragon, Sunfyre at Dragonstone. Rhaenyra is infamously dubbed as "the Half-Year Queen" and "Maegor with teats" for her cruelty.
Aegon II - Two Years
Following Viserys I Targaryen's death, the Greens installed Aegon II on the Iron Throne. HBO's House of the Dragon features his ascension to the crown in episode 9 "The Green Council." He was anointed in front of the masses at the Dragonpit and Ser Criston Cole placed the crown of the Conqueror on his head. Aegon II's rule was disputed by his elder half-sister, Rhaenyra who agreed to strike back at him for usurping her throne. This marked the beginning of the civil war infamously known as the Dance of the Dragons.
Though Aegon and Rhaenyra perish in the Dance, the sister goes first. Aegon is found dead in his litter after being poisoned, allegedly by Lord Velaryon, Larys Strong, and Perkin the Flea. He lacked the qualities that his father, Viserys I, or the king before him, Jaehaerys the Wise possessed. Aegon will spend his reign fighting the Blacks in the protracted civil war.
Viserys II - One Year
The tenth Targaryen king to sit the Iron Throne, Viserys II's reign lasted a year. The crown was passed to him after his nephew, Baelor I Targaryen passed away. Viserys II made several reforms, he also established a new royal mint and made efforts to bolster trade across the narrow sea. Many saw him just as wise and shrewd as the Old King Jaehaerys, but his reign was cut short by a sudden illness. History isn't kind to Viserys II as he's accused of poisoning Baelor to take the throne
Tommen Baratheon - Three Years
Tommen Baratheon inherited the Iron Throne after his brother, Joffrey was poisoned at his own wedding feast by the Queen of Thorns, Olenna Tyrell. While Joffrey's reign is characterized by abuse of power, Tommen was a do-nothing king. He was naive, inexperienced, and in the grip of his shrewd wife, Margaery Tyrell.
Tommen's reign was plagued by the rift between the Faith and the Crown, thanks to his mother, Cersei Lannister who allowed the Faith to re-establish the Faith Militant in a bid to remove the Tyrells from the capital. However, the Faith eventually turned on Cersei, and Tommen accommodated the High Sparrow, announcing the union of the Crown and the Faith. Just when the trials of Cersei and Ser Loras were to take place at the Great Sept of Baelor, an absentee Cersei had the place destroyed by wildfire, thereby eliminating all her enemies. Tommen jumped to his death after witnessing this wildfire explosion.
Daenerys Targaryen - Assassinated After Taking The Throne In 305 AC
Few characters in the Game of Thrones universe have an arc as tragic as that of Daenerys Targaryen. The Mad King, Aerys II's daughter, Daenerys spent her life away from home, enduring all sorts of hardships. However, she brought three living dragons into the world, acquired armies, an armada, conquered cities, advisors, and Dothraki, and finally headed home in Game of Thrones season 6, episode 10, "The Winds of Winter."
Daenerys' war for Westeros didn't go as swiftly as she had presumed. Having made thankless sacrifices throughout, she eventually succumbed to the Targaryen madness. She burned King's Landing to the ground after hearing the bells of surrender ring. Once she declared to "liberate" more lands in her victory speech, her nephew/ lover, Jon found her beyond hope and plunged a dagger into her heart. Daenerys' reign ended before it could even begin, and she's infamously known as the Mad Queen on Game of Thrones.