A petrified shard of Dragon Heart, recovered from the corpse of the Black Dragon in Karkasse Ridgelands. With the right magic, it can be used to grow a powerful Dragon Mount.
Speak to a Daru Priest in Marianople, Austera or Freedich Island to learn about raising Dragons. You may then revive the Dragon Heartshard using Breath of Life, resulting in a Flamebeat Heart, Windsong Heart, or Earthroar Heart.