The source to the fire clad dragon's unusually high temperature is said to be its heart. The heart pumps blood at an extremely high temperature, which then travels all around the body with a temperature as high as lava. Strangely, when this heart is exposed to air, it hardens into something resembling a crystal, and stops moving. Though the heart may stop beating, the mysterious heat that emanates from it is still unfathomable.
A red hot jewel that was once the heart of Claudalus.