Dragon lord Brimstone: The first dragon lord, he reigned sometime around 3000 BLB (Before Luna Banishment). He was the one who brought the dragon together as one people, before him they lived in differents nomadic tribes scattered all across Equestria. To achieve his goal, he had to proove his strength by defeating a mighty earth spirit from which he made the bloodstone scepter. At the end of his life he decreed that his title would be passed on to the dragon who would have proved to be the strongest of all.
 
Dragon lord Garnet : Called the wise due to his vast knowledge of the world and his thought out attitude.  
He was already old when he became dragon lord and only reigned for 100 years but despite his old age and his composed attitude, he was not afraid to fight and won his title by defeating an ursa minor.  
After Brimstone unified the dragons there were still conflicts and infightings between and inside the different tribes so Garnet decided to promulgate laws that all thye dragons, no matter who they were or where they came from, had to follow. Although some of these were modified and new ones were added, most of the original dragon laws are still followed in modern days.
 
*Dragon lord Scintilla :*Up to this point, the dragons were nomads and were travelling around the world according to the season. The dragon migration is the last practice from this time that is still in use today but it’s more by tradition rather than out of real necessity.  
Scintilla wanted to find a land for the dragons to settle in, she raised an army and went at war with the yak who possessed the most territories at this time. Scintilla was merciless in a fight but did show mercy to those who didn’t want to fight and when prince Ulysses aked for peace in exchange for some lands, she accepted although the dragons could have easily took everything by force. She choose a volcanic area, rich in gems, to settle and named it the dragon lands. To thanks Scintilla for her mercy, Ulysses bestowed the title of honorary yak to Scintilla, and declared it a sacred bond.  
A bond that may have transcended death as yak legends says that during the crystal war, the yak were took by surprise by king Sombra forces and would have been wiped out without the intervention of a huge dragon who came from nowhere, repelled the enemy soldiers and bought the yaks enough time to prepare themselves before disapearing without a trace.
 
Dragon lord Celestine: Called the sky dancer, she was a wyvern, a rare dragon subspecies which is characterised by its members having their arms fused with their wings giving them improved performances in the air but poor mobility on the ground.  
She earned her title by flying higher than any other being has done before, to the point that air was so rare that it couldn’t carry her anymore. She reigned for 200 years before relinquishing her position, as she couldn’t bear to stay away from the skies.
 
*Adamor the despiced/the cruel/the merciless:*Formerly known as Adamor the white dragon because of the unusual color of his scales. He believed than dragons were the strongest of all the species of Equestria, a belief shared by all dragons but when most of them would simply ignore other, Adamor wanted to go further, and to either rule them with an iron fist or to kill them all if they resisted, as the weaks only have a choice between servitude or death. He launched multiple attacks on all the denizens of equestria, even the yaks who were regarded as allies since the reign of Scintilla, not to steal their gold or lands as it as bean done in the past, but to demonstrate his strength. Such brutality was too much, even by dragon standards and they tried to force him to give up his powers but it was too late, Adamor was too strong and had found supporters to his cause, this resulted in a war between dragons that had disastreous consequences. Indeed, dragons have a very low birth rate, some of them can’t even have a child during their whole life, it normally make up for their very long lifespawn but with the huge number of death that a war bring, it nearly caused their species to go extinct.  
Adamor was finally killled by Garble, putting an end to the dragon civil war, Adamor was denieded entry to the dragon lords mausoleum and was sentenced to be broken apart so he could never wake up again, but before the sentence was carried out, some of his followers stole the body and hid it somewhere where it was never found.
 
Dragon lord Garble: Called the rightous, he was the one who put an end to the dragon civil war by killing Adamor in a fight that cost him his wings. His spend his life hunting down remnant of Adamor followers and did his best to repair the damages caused to dragons and to other denizens of Equestria. To ensure that another catastrophe lke this would never happen again, he promulgated a law which required the dragon lord candidates to be under 250 years old (the age a dragon become adult) so that if the new dragon lord tryed to abuse his power he could be taken care of easily; and another that put a limit to the time a dragon lord can rule.  
Brimstone, Garnet and Scintilla may be regarded as the founder of dragon civilisation but Garble is without a doubt the most beloved dragon lord of all, and to this day his name his often given to children in memory of the one who saved the dragons and brought back peace in the dragon lands.
 
Dragon lord Plutos: Called the rich, he was driven by an unusually high thirst for gold and was rumored to possess the biggest hoard ever seen, containing riches from all around the world. At some point he tried to steal the Crystal heart from the crystal ponies, and despite the fact he couldn’t keep it for very long and add it to his hoard, the feat was impressive enough to make him the new dragon lord. Surprisingly, toward the end of his life, he gave up all his treasures and disapeared from the dragon lands. The legend says that he had found the greatest treasure of all and went to hide it inside a mountain which he became part of once he died. Although he was greedy he still thought about his subjects well being and established the trial of the gauntlet of fire to prevent young dragon to put themselves in danger while trying to prove themselves in order to become dragon lord. He is one of the only two dragon lords to not lie in the mausoleum of the dragon lords.
 
Dragon lord Cinder: Cinder wanted to become famous and declared war on the great city of Griffonstone which was in its golden age and was the most powerful millitary force of its time. The ponies who were allied with the griffons joined the war too and the yaks sided with the dragons. The war that followed was the greatest in Equestria history and involved all the main nations of Equestria. It generated enought chaos to break the seal that held Discord since the beggining of time which forced the opponents to stop their fight to face their common enemy.  
What would have been the outcome of this war without Discord intervention is hard to say, the dragon had brute strenght on their side as well as the ability to fight both on ground and in the air, but the griffons had strategy and could make weapons unmatched by modern ones, not to mention the magic of the ponies.
 
Dragon lord Torch: Like other dragons, Torch put strength above all but unlike most dragons who tend to disdain other species, he don’t care from who it come, for him strong people are strong people, no matter what they are.  
This is why he could become friend with Celestia after she fought Tirek with him, and later with Luna and Catrina althought he never admited it and always refused Celestia’s offers to form a alliance between ponies and dragons to save face.  
He was called the soft for a while after he married his wife, a dragoness with a poor health and was always sick but had great determination and wouldn’t take no for an answer. Despite her health, she finished the gauntlet of fire just behind Torch, she was half dead but managed to go farther than most healthy dragons, Torch was so impressed that he married her, she died when Ember was born, the years spent to watch over the egg having took their toll on her. After this tragic event, Torch became very protective of her daughter and trying to keep her out of harm even though getting into danger is in dragons nature.
 
Dragon lord Spike: Called the brave and glorious by the crystal ponies. Because he was hatched prematurely by pony magic instead of slowly absorbing magic in the air for decades, he is smaller and weaker than other dragons of his age but being raised by ponies also made him less agressive and more benevolent and open about friendship.  
He had the shortest reign of all the dragon lords, only issuing one order after retrieving the bloodstone scepter and then giving up his position.
 
Dragon lord Ember: The newest dragon lord, she have her mother’s temperament but no her father’s strength. Having been protected by her father since her birth, she tried to prove she was as capable as any other dragon by secretly entering the gauntlet of fire where she met Spike who convinced her to work together to copensate their lack of strength. At first she was uneasy with the idea of friendship and went on her way once they passed most of the obstacles but she latter changed her mind and came back to save Spike from Garble, allowing him to become the new dragon lord. Spike then gave up his title to her, convinced she would not be a menace for the ponies.  
Since then, she tried to learn more about the way ponies do friendship and tried her best to oppen the dragons to the rest of Equestria. She fell in love and married the king of the reformed changelings,a decision which caused a lot ruckus but was received better than she had expected (Torch only tried to kill Thorax twice).
 
Fun fact: writing this description took me longer than the actual drawing.