Xuihcoatl

Xuihcoatl was one of Akasha's creations, long before the establishment of Equestria. He was one of the primordial dragons, ancestor of the current day dragons, but much bigger than any dragon in present time Equestria. 

 

He was taught magic of fire, destruction and chaos by Akasha. He was the first dragon to hold the power of fire, and the one who passed it down to the rest. He was a player in many of the wars between Akasha and Mortina and played a role in many civilizations crumbling at their orders.

 

He served as the dragon king and led the dragons in devastating battles against other creatures in that time.

 

He used magic to cause havoc and destruction, erasing entire civilizations and species from the Earth. Mortina and Akasha would send him to erase whatever creation of theirs they grew bored with.

 

But that's just how his end came. Mortina grew angry with Akasha winning all wars against her creations because she would just send Xuihcoatl instead of fighting fair, so she descended upon the Earth willing to kill Xuihcoatl. He was so full of himself he thought he might be capable of fighting her, and wished to take on her role, but he didn't stand a single chance in front of the Goddess of Death.

 

He took this as a betrayal from the goddesses - Mortina intervening directly was cheating. His soul was outraged, and unable to move on. By anger alone he remained, lingering in between the realms of life and death, even long after any soul would have faded into nothingness.