Chapter 0: Who is Demon King Guduranis?

Author's note: In this chapter, I'll explain the origin and abilities of the fallen demon king, Guduranis.

Short Biography:

Guduranis, a demon king from beyond the stars (as seen by the inhabitants of the world Lambda), launched a war to conquer the world with the help of his evil gods, ancient gods from other dimensions.

Guduranis' corrupted mana gave birth to creatures like orcs and goblins, monsters that didn't exist before in Lambda. He used them to fight the other gods and heroes of the world.

Appearance:

His appearance is indescribable, beyond mortal comprehension.

Abilities:

It was said his power was so great that he could face each of the gods (including the great gods) on his own. Plus, he had a unique ability to break and destroy souls, a power no other god possessed. However, he could only destroy a soul after killing his opponent's physical body. As for gods, he had to weaken them enough first.

Some gods were too powerful to destroy, so he chose to seal them instead, as the war didn't give him enough time.

Guduranis could protect himself with barriers against both physical and magical attacks, a skill similar or identical to the "Dark King's" magic used by Vandalieu (the protagonist of the manga Death Mage).

He also had the ability to mutate parts of his own body to perform various tasks, like hardening his blood or using it to corrupt other creatures and turn them into monsters.

His mutations could also cause extreme fear and contaminate mana through mere eye contact.

Additionally, he created his own transmigration system, allowing souls to reincarnate into monsters born in devil's nests (areas with high mana concentration) and in the world's dungeons.

He is also responsible for creating demons, monsters made of pure mana.

Extra bonus: Demons created from Guduranis' corrupted mana are immortal thanks to his transmigration system. Only Guduranis could permanently eliminate them (and now Vandalieu can too).

The Demon King's "Death":

Guduranis realized that it wouldn't be Bellwood, a hero with exceptional combat skills, but rather Zakkart's knowledge that would one day cause him trouble (Zakkart was a human from Earth who used his knowledge after being summoned to Lambda). Guduranis disguised himself as one of his own soldiers and annihilated Zakkart, along with Solder, Ark, and Hillwillow (other humans summoned from Earth).

Guduranis and his army were only defeated after destroying four of the Eleven Great Gods and gravely wounding the others.

He didn't truly die. His body and soul were divided and sealed into several fragments known as "Demon King Fragments," which, if reunited, could allow him to resurrect.

Author's Note: Yeah, he's OP. For context, the Great Gods in the Death Mage universe are as powerful as Rodcorte, the god of transmigration who manages the souls of multiple worlds.

Legacy [Warning: Spoilers ahead for the light novel]:

After the war with the Demon King, Lambda's population had been reduced to a little over 3,000 humans, elves, and dwarves. The world was largely overrun by devil's nests due to mana corruption. Plus, four of the eleven Great Gods of Lambda were killed during the war, and four of the seven remaining gods fell into a deep sleep, exhausted.

Almost all the monsters present in Lambda today are descended from the Demon King and the Evil Gods he had enslaved.

His transmigration system continues to function, providing souls to various monsters, except for those belonging to the goddess Vida's faction. The semi-conscious fragments of Guduranis' body have also mutated over the millennia, becoming weapons used by different factions in the world.

After his defeat, the remnants of his army split into dozens of factions, with some Evil Gods seeking to rule their own territories or replace their former master.

Some of these gods joined Vida's Faction, while others had already accepted the defection offers made by Zakkart.

Meanwhile, the High God of Law and Light, Alda, adopted increasingly radical measures. He led a genocidal campaign for 100,000 years against all monsters and the descendants of the Evil Gods, in hopes of restoring Lambda to its original state before the Demon King's arrival.

Alda's radical policy sparked significant opposition from other gods.

Guduranis had shattered the souls of the four human champions, forcing Rodcorte, the god of transmigration, to merge those soul fragments, as well as traces of Guduranis' mana, into a new composite entity.

This new soul would one day reincarnate in Lambda as the death mage, Vandalieu.

Finally, a fragment of Guduranis' soul was implanted into the adventurer Edgar in the hopes of empowering him to defeat Vandalieu. But without the god of reincarnation knowing, the Demon King used this opportunity to take control of Edgar's body and attempt to gather the fragments of his soul to return to life.

Author's Note: So yeah, that concludes the summary of the Demon King's abilities and feats. The protagonist has inherited a large portion of the Demon King's powers.