Avel

About
Avel was a dragon, and the second Demon King, created after accidentally consuming the blood of the previous Demon King Kkulf Kkulf.

While his era lasted 721 years, he only experienced 56 of them.

He was the one to slay Demon King Kkulf Kkulf, not through any feat of great strength, but a mere chance attack against an enemy withered and weakened by centuries of war. The blood of Kkulf Kkulf doused Avel, and he became the second Demon King.

Avel was never particularly powerful, in fact he was quite a weak coward, but he was a notoriously tricky and cunning Dragon.

Appearance and Abilities
Avel was an average-sized dark-blue Dragon before his transformation. After the transformation he grew horns, he became larger, his eyes became red and narrow, and four white wing-like protrusions jutted out of his lower neck, these were used for fast flight.

Avel mostly relied on hiding and planning against his enemies during his short time as Demon King, while his hatred for the Dragons was great, he was not foolish enough to perform a full-frontal assault on them. Because of the indirect approach Avel took, the Dragons didn't really bother with him, Dragon King Magiihoa did not see Avel as much of a threat and thought little of him.

That all changed when Avel kidnapped Magiihoa's wife, Kamilla, and transformed her into a Dark Lord. Kamilla was the only female Dragon and she was property of the King, not only had Avel ended any chance at future offspring for the Dragon race, he had angered the Dragon King directly by completely ignoring the Dragon duelist code:

"If you wish to claim the female Dragon, you must engage in an honorable duel with her husband, the victor claims her as his own and gains the title of Dragon King"

Because Avel had sneakily disgraced the Dragon people, Magiihoa gathered the entire species for an assault on Avel's keep, Magiihoa himself was the one to directly confront Avel, their battle ended with the Demon King sealed in a dark, inescapable pit.

After this, the Dragons made the best of their situation and founded the united continental kingdom of Tron, where there was no conflict, no war, no discrimination, the world was a blissful paradise.

Ludo-Rathowm sent Ragnarok and the Angel Knights to purge the world soon after, and Ssulal was selected by Planner to be the next Demon King.

It should be noted that while the world was purged, no trace of Avel was ever recovered, leading some to speculate whether or not he was killed, though it's likely he was reduced to the Blood Pool by Planner.

AV - Avel's Era
AV0001 - Demon King Kkulf Kkulf is slain, Avel becomes the new Demon King.

AV00?? - Avel turns Megallas into a Dark Lord as a joke.

AV00?? - Avel kidnaps Kamilla from the Dragon King castle. Kamilla was the only female Dragon and she belonged to Magiihoa.

AV0011 - Because Avel had violated a sacred Dragon rule, the entire Dragon tribe waged war on him, the "Final War" begins.

AV0056 - The "Final War" ends, Avel is sealed in a dark prison.

AV0060 - Ludo-Rathowm yawns.

AV0061 - Ragnarok and the Angel Knights initiate the apocalypse protocol. Dragons are slowly hunted down over the course of 700 years.

AV0721 - Roven-Pan creates the third Protagonist Race, "Humans". Ssulal is appointed the title of Demon King.

Known Dark Lords Created: Megallas, Kamilla.

Preceded by: Demon King Kkulf Kkulf.

Succeeded by:  Demon King Ssulal

Trivia

 * He's usually seen as the most pathetic Demon King among the fanbase.
 * His era was the second shortest of all Demon Kings.