Great War

The Great War (大戦) is a worldwide conflict that occurred during the Mythical Age, between the demon kingdom of Dilhade against the alliance of the human continent of Azesion, the spirit forest of Aharthern, and the divine realm of Azure Sky of the Gods.

Summary
The war went on for so long that the reason why they were even fighting was lost. No one knows if it was humans or demons who made the first move. But once it happened, it began a cycle of murder, revenge, retaliation, and death. Humanity, who was naturally weaker than the demon race, received support from the spirits and gods. Likewise, the demons who constantly fought one another banded together against their common foe.

History
During the highpoint of the Mythical Age, various demons fought amongst each other in order to become the ruler of their race. Many of them invaded Azesion in order to expand their own domains. The fire of war embraced them both inside and outside the country, and each demon was forced to fight their internal enemies as well as independently deal with the more organized and united humankind, and the spirits and the gods who assisted them.

Humans and spirits feared that the demons would become united, because it was the demons' internal conflicts that made it possible to maintain the balance of power between Azesion and Dilheid in equilibrium. If the demons had a single ruler that would be able to unite the entire race under one banner, the course of conflict would instantly overturned.

Azesion's army continued to cunningly sow the seeds of distrust in the rulers who dominate the various regions of Dilhade. By forcing the demons to fight each other, they planned to increase the advantage in the Great War as the demons underestimated humankind by considering them to be insignificant race. The humans were able to influence the course of hostilities and their goal slowly but surely bore fruit.

Over the course of the Mythical Age saw the rise of many powerful "king-class" demons, who possessed enough power to rule over a domain of Dilhade, as they raised armies to battle their enemies to seize full control of Dilhade and crush the enemies of the demons. The most prominent and powerful of these were the Four Evil Kings: the Conflagration King Eldmed Ditigeon, the Netherworld King Aeges Code, the Cursed King Kaihilam Jiste and the Scarlet Stele King Grysilis Derro.

However, one more contender emerged from the shadows. This figure was the Demon King of Tyranny Anos Voldigoad, who soon became known as the most powerful demon in Dilhade. He and his army succeeded in bringing down the Sun of Destruction, as Anos turned the Goddess of Destruction Abernyu into his Demon Castle Delsgade, which he built in the city of Midhaze. Afterwards, he and his army repelled the armies of other demons who attempted to conquer the city of Midhaze in the aftermath of Sorcerer King Bomiras Heros' death, as Anos brought city under his control.

Meanwhile, in order to respond to the rise of the Demon King Anos, the humans formed the Demon King Subjugation Battalion, an elite army created to battle and defeat the Demon King. While choosing who would become the leader of the army, many advocated for the selection Hero Kasim, on the account of his superior swordsmanship and command over holy magic. However, Kasim proved incapable of lifting and wielding the legendary holy sword: Evansmana, the Sword of Three Races, which was the Demon King's sole weakness and the one thing that could permanently slay him. Ultimately, Kasim's junior, the Hero Kanon proved capable of wielding Evansmana and became the leader of the Battalion, as he lead them in countless battles against Demon King Anos and his army.

During one battle, Anos was able to corner Kanon, but the latter managed to force him to retreat despite being put in an unfavorable position. Over the course of the war, Anos and Kanon gained an unspoken respect for each other, as Anos became fascinated by Kanon' courage and strength of will, deeming him to be the only one worthy of being called a Hero.

Eventually, after conquering all of Dilhade and overthrowing the Four Evil Kings, Anos was able to forge a reluctant alliance with them against their common enemies, as they joined forces to fight against humankind and their allies. While the humans were able to push into Dilhade and seize some demon territory, the humans slowly found themselves overwhelmed by the united demon race, with only the capital city of Gairadite repelling demon onslaught, due to being a under the command of Hero Kanon.

Despite the tide of the war turning in his favor, Anos was dissatisfied with the constant carnage and death of the war on both sides, so he sought a way to end the war on peaceful terms. He approached the Great War Tree Migelonov in order to gain wisdom and find a way to end the war. Afterwards, he created the Seven Demon Elders to serve as a facet of his plan.

Anos sought out the Goddess of Creation Militia, the only god who remained neutral during the Great War, whom he had befriended prior. She was also trying to end the war peacefully, although she wasn't capable of accomplishing it due to her nature as a god, with Anos offering his cooperation to her and explaining his plan.

After that, he sought out the Great Spirit Reno, as he saved her from being used by the Heavenly Father Nosgalia, who was trying to create a Child of God that would destroy Anos. Deciding to trust Anos' offer to end the war, she was invited to the Demon Castle Delsgade, as Anos left his right-hand man Shin Reglia to serve as her bodyguard for the journey.

Finally, Anos alone made his way to Gairadite, in order to seek out Hero Kanon and gain his cooperation for his plan. But Anos was attacked by the human king Jerga, who wanted to kill Anos for causing his family's death, although Anos easily defeated him and quickly reminded him that Jerga wasn't the only one that experienced tragedy, as Anos was born from his mother's corpse after humans killed her. Anos then told Kanon to come to Delsgade to continue their talk about ending the war.

Aftermath
Kanon, Militia and Reno made their way to Delsgade, where Anos revealed the specifics of his plan to end the war. They would combine their powers and by Anos converting his life into magic power, they could activate a grand barrier spell known as Beno Ievun to separate the world into four realms for a millennium until the hatred between the races subsides. While Kanon was initially a bit hesitant, he ultimately agreed with Anos' suggestion. Reno and Militia combined their powers to feed magic power into Anos' body, while Kanon stabbed him with his holy sword to transfer its vast power and his own magic power into Anos. Before Anos perished, he and Kanon exchanged a vow to be friends in their new lives. Unable to withstand the enormous magic power, Anos lost his body and began reincarnating, signaling the end of the war.

Two thousand years later, an attempt to restart the Great War was made by a radical group of humans led by the fallen Hero Jerga with the aid of the Heavenly Father God Nosgalia.

Trivia

 * It was stated that Hero Kanon encountered and battled against all of the Four Evil Kings, though the exact details of those encounters is unknown.