This achievement is unlocked by completing the Epic Dungeon called Malabog's Castle. The Epic dungeon culminates with a battle with Malabog and soon after Valindra's Blue Dragon called Fulmninorax, once the Dragon is dead the achievement will be yours. There are two requirements to enter this Epic Dungeon. The first thing is that you need to be level 70. Secondly you need to have a total item level of 1600. This can be found on your character sheet on the bottom left of the screen and to the right of your rotatable character.