Arrax

"Arrax was struggling to stay aloft in the gale when a roar shook the very foundations of Storm's End."

- - Robert Baratheon Arrax was one of the dragons that belonged to House Targaryen, which fought during the great civil war known as the Dance of the Dragons, during which it was the mount of Rhaenyra Targaryen's son Lucerys Velaryon.

Biography
Arax was one of the twelve dragons, on the island of Dragonstone and one of the six who had a rider. Arax's was Prince Lucerys Velaryon. During the House Targaryen civil war, known as the Dance of the Dragons, on Rhaenyra Targaryen's orders, he flew the young prince to Storm's End in order to gain the support of Borros Baratheon, the Lord Paramount of the Stormlands. However, after arriving, Borros almost immediately sent Lucerys away, having already made a pact with Aemond Targaryen. During their way back to Dragonstone, a storm began just after they rose into the sky. Arax was struggling, as Aemond arose on his dragon Vhagar, who was five times the size of Arax. As the castle watchers of Storm's End looked up at the sky, it was illuminated by a single flame, and then followed by a shriek that even drowned out the thunder. Then, Vhagar clasped his teeth around so hard around Arax's neck, until he was decapitated. His rider would later fall from his mount and drown in Shipbreaker Bay.

In the books
Princess Rhaenyra Targaryen's three eldest sons (each by Laenor Velaryon) were Jacaerys (born 114 AC), Lucerys (born 115 AC), and Joffrey (born 117 AC). The rival faction at court who supported her stepmother Alicent Hightower and her children spread the accusation that Rhaenyra's three sons were not really Laenor's, but bastards fathered by Harwin Strong. In an effort to confirm that he considered Rhaenyra and her sons the true heirs to the throne, her father King Viserys II decreed that a dragon egg would be put in the cradle of each of the boys, to bond with the dragons that hatched from them. Those who doubted the paternity of Rhaenyra's sons also doubted that the eggs would ever hatch, but they were quickly disappointed, as each of the eggs soon hatched in turn. The hatchlings were named Vermax (bonded with Jacaerys), Arrax (bonded with Lucerys), and Tyraxes (bonded with Joffrey). The exact date each hatched is not known but the last seems to have hatched by no later than about 120 AC.

At the start of the civil war Prince Jacaerys flew north as a messenger on Vermax. Arrax and his rider were slain by Prince Aemond Targaryen and Vhagar in the skies over Shipbreaker Bay. Three days later, the dragon's head and neck washed up beneath the cliffs below Storm's End, along with Prince Lucerys' corpse.