Quicksilver was a dragon rode by King Aenys Targaryen, and later by his son Aegon Targaryen. He perished alongside his rider at the hands of Balerion and Maegor the Cruel, during the Battle Beneath God's Eye.
Quicksilver was born after the War of Conquest and ridden by Aenys I, later by his son Aegon. When Maegor usurped the Throne, Aegon began gathering as many lords as possible to his cause, rallying them behind Quicksilver. Aegon and Quicksilver where confronted at the God's Eye by Maegor and Balerion, and despite not being a very young dragon, already over 20 years old, he was no match to the much older and bigger Balerion, who was now over a hundred years old, and both died very easily.