Prince Lucerys Velaryon, also known as Luke, was the second-born son of Princess Rhaenyra Targaryen and her first husband Laenor Velaryon. He was a dragonrider, his dragon was Arrax. He was a strong strapping lad, skilled in arms.
Prior to the civil war Lucerys had long served as a squire. He was fourteen-years-old at the start of the civil war.
Luke was sent on a mission that was considered shorter and safer than his brother Jace's - he flew on dragonback as a messenger to Storm's End where it was expected that Lord Borros Baratheon would give him a warm welcome. Prior to his mission he swore on the Seven-Pointed Star to his mother on Dragonstone that he would take no part in fighting.
Once at Storm's End tragedy befell Lucerys. Ill chance brought two princelings together - Luke and Aemond One-Eye. Prince Aemon had arrived at the castle on Vhagar before Luke.
Upon his arrival in the Round Hall, Luke ignored Prince Aemond and went to deliver his letter to Lord Borros. Prince Aemond attempted to snatch the letter but Lord Borros roared a command and his knights intervened, pulling the princelings apart.
After Borros's maester had whispered the message contained in the letter to him he asked Luke "And if I do as your mother bids, which one of my daughters will you marry, boy?" he then told him to pick one of his four daughters standing in the Round Hall. Prince Luke had to admit that that he was betrothed to his cousin Rhaena Targaryen. Lord Borros replied that he thought as much and told him to go home.
As Prince Lucerys turned to take his leave Prince Aemond drew his sword but Prince Lucerys recalled his promise to his mother and told Aemond that he would not fight him and that he came as an envoy, not a knight. When Aemond grew angry, telling Luke that he would have his life, Lord Borros grew uneasy and put guards between the two princelings.
Lucerys Velaryon was escorted back to the castle yard where Arrax awaited. The dragon was hunched down in the rain. In the Round Hall, Prince Aemond again asked Borros for his leave. Lord Borros let him go once Lucerys had taken off.
Outside a terrible storm was raging, bad weather for flying. Arrax was struggling to stay aloft as Aemond mounted Vhagar and went after Luke. Arrax was younger and swifter, and on a calm day might have been able to outfly his pursuer, but the weather impeded him and Vhagar was five times the size of her foe and the hardened survivor of a hundred battles. The two dragons met above Shipbreaker Bay. According to Archmaester Gyldayn, if there was a fight it could not have lasted long.
Arrax fell, broken, to be swallowed by the storm-lashed waters of the bay. His head and neck washed up beneath the cliffs below Storm's End three days later. Prince Lucerys's corpse washed up as well.
On Dragonstone, Queen Rhaenyra collapsed when told of his death and Luke's younger brother Joffrey swore a terrible oath of vengeance against Prince Aemond and Lord Borros. As the black council sat to consider how to strike back, a raven arrived from Harrenhal. "An eye for an eye, a son for a son," Prince Daemon wrote. "Lucerys shall be avenged".