The central tragedy of House of the Dragon hinges on a series of escalating missteps and betrayals:
Season 1: King Viserys names Princess Rhaenyra his heir following Queen Aemma's brutal death during a forced C-section. To secure her position, Rhaenyra marries Laenor Velaryon, but mothers three sons (Jacaerys, Lucerys, Joffrey) whose obvious physical resemblance to Ser Harwin Strong sparks persistent bastardy rumors. On his deathbed, a delusional Viserys whispers to Alicent about Aegon the Conqueror's dream. Alicent misinterprets this as a mandate to put her son, Aegon II, on the Iron Throne. The Greens quickly usurp the crown. Rhaenyra attempts diplomatic negotiations, but when Aemond's dragon Vhagar kills Rhaenyra's young son Lucerys over Shipbreaker Bay, war becomes inevitable.
Season 2: Daemon hires assassins ("Blood and Cheese") to avenge Lucerys, leading to the murder of King Aegon II's young heir Jaehaerys in the Red Keep. In response, Aegon hangs every ratcatcher in the city. At Rook's Rest, Aemond secretly turns on his brother Aegon II during a dragon battle, allowing Vhagar to burn Aegon and Sunfyre while killing Princess Rhaenys. Aegon is left disfigured, and Aemond takes power as Prince Regent. Seeking to match the Greens' dragon power, Rhaenyra recruits lowborn dragonriders ("dragonseeds").
Season 3: The war reaches full scale with the Battle of the Gullet, where the Triarchy fleet ambushes the Velaryon fleet, claiming Jacaerys Velaryon's life. Ser Criston Cole meets his death in battle, while Aemond forms an alliance at Harrenhal with the mysterious Alys Rivers, discovering old dragon eggs while abandoning King's Landing to Rhaenyra's advancing forces.