Hellkite

One of three known Ancient Dragons — alongside the Lightning Dragon Behemoth and the Ice Dragon Xavier — created by the Gods to protect Antaria. Not immortal, but ageless, having lived since the beginning of time. Guarded a Destroyer Statue in the volcanic region of northern Geysir since the end of Ragnarok.

Slain there in 1205 E.C. by Karls Brandt, sent by Beradin to retrieve the statue — the kill that earns Karls the title 'Dragon Slayer.' Killing Hellkite left a permanent black stain on Karls's sword, Giga Death, that has never come out; Hellkite's spirit is said to linger in the blade ever since, and Karls later shows strange symptoms tied to an ailment linked to the kill (Chapter 8).