Born in 10 A.D., Quicksilver was a dragon, apparently female, ridden by King Aenys I Targaryen, and later by his eldest son Aegon the Crownless, in the early first century after the Conquest. He died in the year 43 during the battle under the Œildieu.
The scales of Quicksilver seem to have been white. His fire was pale white and he was four times smaller than Balerion in the year 43 when he died.
King Aenys I Targaryen
When the egg of Quicksilver hatches in the year 10, the little dragon is given to the young prince Aenys Targaryen, the eldest son of Aegon the Conqueror born in the year 7, thus silencing the rumors that he is not Aegon's son, but a bastard born of Queen Rhaenys and one of her lovers.
Quicksilver is Aenys' favorite mount. In the year 23, the dragon carries him to Dorne, to celebrate the ten years of peace between the principality and the Seven Crowns.
In the last years of King Aegon I's reign, Aenys and Thief-Silver replaced the king in his usual royal travels, which allowed him to meet his people and make them know and love him.
The dragon and his dragonlord are in Highgarden in the year 37 when the news of Aegon's death reaches them. Aenys rides Silverthread to return to Peyredragon, attend his father's funeral and be crowned King of the Seven Crowns.
While Aenys I Targaryen's reign is just beginning, the rebel Harren the Red seizes Harrenhal. Lord Tully asks the king to burn the castle with his dragon, but Aenys refuses.
A few years later, he does not use his dragon against the Great Septon of Villevieille at the beginning of the War of the Faith. In the year 41, the king fled to Peyredragon, where he died early the following year.
Quicksilver lights the funeral pyre of his dragonlord. According to some chronicles, the dragons Vermithor and Silverwing add their fire to that of Quicksilver.
Prince Aegon the UncrownedAfter the death of Aenys I in the year 43, Vif-Argent was taken over by his eldest son, Aegon the Crownless. The latter took advantage of the absence of the usurper Maegor I Targaryen to infiltrate King's Landing with his sister-wife Rhaena, and retrieve the dragons Flintstones and Silver Snitch.
They fly together to Castle Rosieres, where they gather an army to defeat the usurper. Mounting Vif-Argent, Aegon himself leads his ost through the Conflans. Arriving at the Œildieu, they are surrounded by Maegor's supporters.
The pretender Aegon mounts his dragon to lead the offensive, but his uncle appears on Balerion. A terrible battle begins in the air and on the ground. Older, bigger and more ferocious than Quicksilver, Balerion engulfs his pale fireballs in mighty sprays of black fire.
Finally, Maegor's dragon closes his jaws on his opponent's neck, tearing a wing from his body. Screaming and smoking, Silverthread collapses to the ground with his dragonlord, where they both die.