X'rphan the White Wyrm

The Frost Dragon is a high-level monster from Sword Art Online. It can be found on Floor 55 deep within the West Mountain. It is said that to produce a rare mineral called «Crystallite Ingot», which is formed inside its body and can only be obtained in the presence of a master smith.

Sword Art Online
Kirito and Lisbeth attempted to obtain a Crystallite Ingot from the Frost Dragon to forge a new sword for Kirito, but the Dragon proved to be quite difficult to handle and they were both thrown inside its lair, a giant hole in the ground, which was too deep to climb out of and had an anti-crystal field, preventing the use of teleportation crystals. After spending the night together, they managed to find the mineral, which turned out to be the dragon's excrement, buried in its lair. When the dragon reappeared, Kirito and Lisbeth rode on its back to escape its lair.