Aemond Targaryen, also known as Aemond-One-Eye and Aemond the Kinslayer, was the second son of Viserys I Targaryen and Alicent Hightower. When 10 he decided to claim the dragon Vhagar, currently the largest and oldest dragon. He pushed his half-nephew Joffrey Velaryon into dragon droppings to avoid being caught. After riding Vhagar, he fought Joffrey's elder brothers, Jacaerys and Lucerys Velaryon, and Lucerys cut his left eye out. Aemond later claimed it was a fair trade for Vhagar. He wore a sapphire in place of his eye. During the Dance of the Dragons he supported his older brother, King Aegon II Targaryen.
When Viserys died, Aemond's elder brother Aegon II Targaryen declared himself King, even though Viserys had proclaimed his daughter from his first marriage, Rhaenyra, as heir, beginning the war known as the Dance of the Dragons. Aemond was sent to Storm's End to win the allegiance of Lord Borros Baratheon by wedding one of his four daughters. Lucerys was also sent to Storm's End on his dragon Arrax, having sworn to act peacefully. Borros refused to accept Rhaenyra, and Borros forced him from the castle. Aemond pursued his nephew's dragon on his, slaying them both. This began the hostilities in earnest.
When Aegon was wounded at Rook's Rest, Aemond became regent. He led a force to take Harrenhal, which had been taken by Rhaenyra's husband/uncle Daemon. However, in the process he left King's Landing undefended enough for Rhaenyra to take it, at which she executed Alicent's father Otto Hightower. After this, Aemond rode Vhagar around the Riverlands, burning settlements aligned with Rhaenyra.
Finally Daemon decided to return to Harrenhal on his dragon Caraxes and wait for his nephew. Aemond arrived with his pregnant lover Alys Rivers. Daemon and Aemond then rode their dragons over the Gods Eye. Caraxes suddenly attacked Vhagar from above. Daemon then leapt from his dragon and drove his sword Dark Sister through Aemond's blind eye. Aemond was still chained to the saddle when the dragons hit the water a moment later. His body was later recovered, with Dark Sister through his eye. Daemon's body was never recovered, though it is very likely he died.