Arrax hatched from the egg King Viserys I ordered laid in the cradle of Prince Lucerys Velaryon, Rhaenyra's second son, and was thriving and growing by 129 AC, strong for his years though only a fifth the size of Vhagar. The published books never name his color; the author's own answer to an illustrator was pearlescent white, with a golden chest, golden eyes, and yellow flame.
At the outbreak of the Dance of the Dragons Lucerys, thirteen, swore to his mother that he would not fight and flew Arrax to Storm's End to ask Lord Borros Baratheon for his swords, only to find Prince Aemond Targaryen already in the hall. Borros would allow no blood beneath his roof, so Aemond followed on Vhagar into the storm that had broken over the bay. Watchers on the walls saw distant blasts of flame above Shipbreaker Bay and heard a shriek louder than the thunder, then the two dragons locked together with the lightning around them; if there was a fight, Archmaester Gyldayn writes, it cannot have lasted long. Arrax fell broken into the storm-lashed water with his rider, and the death of the boy prince made the war a war.