Massacre at Kazte Plains was an event that took place during the Annual War between the Re-Estize Kingdom and the Baharuth Empire. It is also when Ainz Ooal Gown and the Sorcerer Kingdom officially debuted themselves to the world.
Prior to the massacre, the Baharuth Empire received word of a tomb that has mysteriously appeared within the borders between their nation and the Re-Estize Kingdom. The Empire has sent Workers to investigate the tomb and report back what they may find but they never returned. Instead, two Dark Elves appeared at the castle, revealing themselves to be members of the Great Tomb of Nazarick. After killing many of the Empire's men including one of the Four Imperial Knights, the Elves demanded the ruler, Jircniv Rune Farlord El Nix to come to visit the tomb and apologized to their king, Ainz Ooal Gown for the transgression otherwise the Empire will pay the price for refusing to comply with their nation's destruction.
Jircniv and his entourage arrived at the Great Tomb where they encountered and taken aback by many of the strange denizens that lived there and the power they wielded. Ainz Ooal Gown, in particular, showed his ability to raise the dead and converted them into undead warriors with supernatural ease. In addition, he possessed a vast military force and beautiful women that will put all of the New World to shame. The Emperor seemingly accepted this and proposed to Ainz an alliance between their nations which the latter agreed but after Jircniv left, in truth, he has already deemed the Elder Lich-like being a threat not just to his Empire but to the entire world and planned on using their alliance to leak information to the other Kingdoms and unite them against him and using various schemes to undermine him. Unbeknownst to him, one of Ainz's men already deduced Jircniv's treachery and informed this to his king.
At the Re-Estize Kingdom, King Ramposa III and his court were informed about Ainz Ooal Gown's existence and his participation to the Annual Wars as an ally to the Baharuth Empire. Terms had been made that should the kingdom surrendered, they must offer E-Rantel to Gown. Despite Gazef Stronoff's warning them about the dangers of the magic caster, both the Noble and Royalist factions dismissed him with only the king and Marchioness Raeven accepting what the Warrior Captain has told them. Nonetheless, the kingdom refused to lose part of their land and decided to continue the war by conscripting many of their male citizens to counter Ainz Ooal Gown.
Following this, Gazef met up with Brain Unglaus and Climb. Gazef asked what the two had been doing throughout the day. Brain and Climb explained that they traveled to E-Rantel in hopes to meet Momon and discuss about the two vampires he was hunting. Unfortunately, he wasn't there as he was taking on a high-rank request much to Gazef's disappointment who thought that the Raven Black Hero can be of help to repel the Empire and Ainz Ooal Gown. During their conversation, Climb informed them that he will be wearing his usual armor despite the obvious disadvantages it presented under orders of his mistress, Princess Renner who was secretly working with Ainz to spare the young knight from harm. Gazef gave the same advice he said to the court about Ainz Ooal Gown to his comrades and the two will made sure to prepare themselves whatever would throw at them by the man who saved Gazef's life. Gazef then mused to them that should all three of them survived, they should have drinks.
Meanwhile, King Ramposa had sent his son, Barbro to head to Carne Village. The reason for this was to gather information about Ainz so that the Re-Estize Kingdom can offer a peaceful resolution to the man and Ramposa secretly wanting to spare his son from death. This action proved fatal as Barbro disobeyed his father and had the village be attacked by his men so that he could use the people as hostages to have Ainz surrender. The people of Carne Village are understandably angered at this and chose to fight on behalf of the magic caster who was their savior, summoning the Goblin Army that wiped out many of their enemies. Barbro and his men retreated in terror. Later that night, Lupusregina Beta visited Barbro who begged to be spared but this is met with deaf ears as the Battle Maid explained that her king has deemed the First Prince useless to his plans and must be punished for his actions. Goblins slaughtered what was left of Barbro's army and the prince died thirty minutes after Lupusregina tortured him.
At the Imperial Castrum, Nimble Arc Dale Anoch and the Imperial Knights awaited for Ainz Ooal Gown's arrival, under secret orders by Emperor Jircniv to spy on the magic caster and determine his power. Piecing together what he had seen, the Emperor believed that Ainz Ooal Gown can at least kill a thousand men and using that theory, he decided the best course of action is to request Ainz to use his strongest spell and show the world the threat that he posed. After that, Nimble and the Imperial Knights will push away what remained of Re-Estize's army. Ainz Ooal Gown finally arrived along with his escort, Mare Bello Fiore. Ainz was also eager to follow Jircniv's suggestion. His main goal was to learn the existence of other Players like him and hopefully, one might be his comrades. He will reveal himself out in the open all while performing the spell. This tactic is to draw out anyone who recognized the spell and deploy the right countermeasures to prevent it. That will confirm Ainz's questions. After greeting his allies, Ainz ordered his army to come and much to the Imperials' shock, the army was comprised of Death Knights and Soul Eaters, monsters in legends that have wiped out entire countries.
The Annual Wars has begun. The Re-Estize Kingdom arrived on the battlefield, bringing in their Royal Army comprised of 245,000 soldiers. Standing at the front lines for the army were Gazef Stronoff and the nobles who acted as the commanders such as Marquis Raeven and Marquis Boullope. On the side of the Baharuth Empire, six legions of the Imperial Army were brought to confront them. The only one that has yet to appear was Ainz Ooal Gown.
Due to possessing superior numbers, most of the nobles of Re-Estize believed that victory was within their grasp. However, King Ramposa III truly felt that the high morale within his forces did not inspire his confidence about the war. In hoping to turn the tide to their favor, the king bestowed Gazef with four of the five National Treasures of the Re-Estize Kingdom. The Warrior Captain possessed the following items; the Gauntlets of Vitality, granting the user endless stamina, the Amulet of Immortality, providing regenerative abilities, the Guardian Armor, resisting lower-level Death Magic and Razor Edge, a magic-enhanced blade that can cut through armor.
So far, both sides has yet to engage the other. Gazef notices this and easily deduced what that meant.
Some time passed, the Imperial Army started to move but instead of engaging the Royal Army, they were merely moving aside to allow their base's main doors to open. Monstrous creatures began to march out. The Royal Army were at lost for words as they stared upon 200 Death Knights and 300 Death Warriors, all mounted on 500 Soul Eaters. The Empire were trying their best not to panic from being scared by their allies. Three people were left to exit the Imperial Castrum; Nimble Arche Dale Anoch, Mare Bello Fiore and the Sorcerer King, Ainz Ooal Gown. Gazef grimaced upon seeing his former savior while most of the Royal Army began to realize the sheer magnitude of the truth behind Gazef's words.
Suddenly, a series of giant magic circles appeared and surrounded Ainz and his escorts who had just stepped onto the front lines. Marquis Raeven understood that this was an unwinnable fight for Re-Estize and decided to return to his unit and declare a full retreat. Gazef agreed with Raeven and the Warrior Captain stayed behind to protect King Ramposa and the Royal Army from the attack. However, Marquis Boullope foolishly led his left-wing of 70,000 men to charge at the Imperial forces.
Ainz observed the scared and confused reactions of the Royal Army and confirmed that there are no other Players present. He had already prepared a Cash Item to accelerate the process of his super-tier magic. Looking back about his plan, Ainz had thought about the massive casualties that was about to take place but he truly felt nothing about it, whether it was because held no personal attachment to most of Re-Estize or his time with Nazarick and this world has started to take effect on him. Still, his mission was clear. He has to take action to allow himself and his tomb to prosper. Crushing the Cash Item in his hand, Ainz Ooal Gown unleashed the super-tier magic spell 'Ia Shub-Niggurath'. A dark wave burst forth from him and headed toward the Royal Army's left-wing. In an instant, the wave killed Boullope and his men whose corpses fell to the ground.
Both the Re-Estize Kingdom and the Baharuth Empire stared in horror at what remains of the former's left-wing. Ainz noticed Nimble's look of fear and asked if anything was wrong. Nimble calmed himself and explained that he was surprised how effective the super-tier magic spell was, killing 70,000 men in a matter of seconds. Suddenly, Ainz laughed at that statement. Nimble turned around and apologized, hoping he did not offend him. Ainz corrected Nimble that the event that he watched was only part of the spell. The spell required sacrificial offerings as fuel to complete it. Now that it was done, the real spell was about to start much to Nimble's growing fear.
Up at the clouds, a black sphere appeared above the corpses of the left-wing. It dropped onto the ground and began consuming all of the bodies. When it was done, taking its place were eldritch abominations that looked like black mass with elephant-like legs, human-like teeth and dozens of tentacles covered over their bodies. Ainz revealed to his allies that they were called Dark Young and he was surprised that he has summoned five of them, an achievement surpassing the one that has summoned two. Only Mare truly praised his king while others tried to hide their discomfort. Satisfied that he has achieved such a momentous accomplishment, Ainz decided not to send them away and had ordered the Dark Young to attack the Royal Army but spare four individuals their master has selected.
The Royal Army were left paralyzed, confused at what they had just seen. Eventually, their commanders managed to order them to ready their weapons and form a spear wall to attack. The Dark Young were too strong and they easily snapped off the pikes of the spears. What was once thought to be a battle turned into a massacre. The Dark Young wiped out hundreds after hundreds, either using their massive hoofs to trample on the humans or their tentacles to flung them into the air. When the Dark Young charged right into the heart of the army, everyone, noble and soldier, abandoned their duties and ran for their lives in a futile attempt to escape. The bloodcurdling screams were everywhere followed by the sound that can only be described as "Splat!." This was a process repeated over and over again across the battlefield.
Marquis Raeven ordered his men to retreat. He could only curse himself for not realizing enough the power of Ainz Ooal Gown who he deemed a monster that must be stopped otherwise the future of Re-Estize will fall apart. Then, one of the Dark Young started following them. Left with no options, Raeven's team of Ex-Adventurers stayed behind to fight it and sacrificed themselves to allow a regretful Raeven the time to escape from its pursuit.
The Empire watched the slaughter, trembling in terror. They no longer cared that the Re-Estize Kingdom was their enemy and only begged all of them to escape. Ainz declared the charade was over and the Empire turned to him as he revealed his true skeletal appearance. He then demanded applause for his might that he brought upon the Katze Plains. Mare clapped in ecstatic joy for his king and soon, the Imperial Army reluctantly joined as well. Suddenly, one of the Dark Young was heading back toward the Imperial Castrum resulting in the Imperial Army to lose their will to fight and fled with a portion of the soldiers trampled to death by their own scared comrades. Nimble was the only one that stayed. Because of this act, the Empire has breached the agreement they made with Ainz but he was in a joyful mood and excused it. The Dark Young arrived and lifted its master onto its back, intending to transport him through the terrain and allow him to finish wiping out the remaining enemy forces.
The Re-Estize Kingdom was left in disarray. The surviving nobles had run away leaving only King Ramposa and what remained of the Royal Army to defend themselves against Ainz Ooal Gown. Brain and Climb managed to survive the assault and reached Ramposa's camp. Together, they decided that the king must be escorted out of the battlefield. Brain and Climb chose to distract the Dark Young allowing the others the time to escape. Before they left, Brain asked a reward for Climb and that should they survive the onslaught, his friend will have Renner's hand in marriage much to Climb's embarrassment and King Ramposa's delight who agreed with the terms.
Outside, Gazef head into battle to confront the abominations to save the men and his king. Gazef swung his Razor Edge and hit a Dark Young's leg. The Dark Young were barely harmed by this and kicked Gazef away. Tried as he could to halt their advancement but despite being bestowed with powerful items, Gazef was no match against the Dark Young. Before Gazef could fight once more, the Warrior Captain witnessed Ainz Ooal Gown riding on top one of the creatures that was heading towards him. He also realized his savior's true identity as an undead being. Brain and Climb reunited with Gazef and prepared to fight alongside him but they didn't have to as Ainz had ordered the Dark Young to halt.
Reaching his destination, Ainz levitated from the Dark Young and landed on the ground below. The Sorcerer King and Warrior Captain exchanged greetings, both felt it has been a long time they had seen each other. Still confused, Gazef asked why Ainz was here. The latter answered that he wanted to offer the man a deal; that he swore allegiance to him and in return, the assault by the Dark Young will cease. Gazef, however, was not able to do that, refusing to betray his kingdom and knowing that this will lead the nobles to take serious actions against King Ramposa and the commoners. Instead, Gazef refused Ainz's generous offer and then pointed his sword at him, demanding a duel against the Sorcerer King.
This left Gazef's comrades and even Ainz to be shocked at what the man was doing. He knew a challenge against Ainz Ooal Gown was suicide and despite multiple warnings by his superior opponent and Brain offering to join alongside him, Gazef stayed with his vows. Ainz could only sigh as he saw it was pointless to change Gazef's mind and reluctantly accepted the duel which he called 'PVP'. Additional terms and preparations were made: Brain and Climb act as an audience to the duel with the latter responsible for signalling the fight and the Razor Edge was inspected of its potency by Ainz to ensure the duel's requirements were met which was confirmed. In addition, should Gazef perished, he wished not to be resurrected; Ainz agreed to it.
With that, Climb rang the bell and the duel started. Gazef charged right at Ainz but nothing happened. Everything came to a halt as if time has stopped. All living beings were frozen like statutes except Ainz Ooal Gown. Ainz revealed to the unknowing Gazef that during 'PVPs', time spells existed and one must prepare counter spells should they be used. The magic caster said his farewells to the Warrior Captain before using the high-tier spell, [True Death], killing Gazef Stronoff.
When time resumed normally, Brain and Climb watched as Gazef suddenly fell. The two did not know what happened and beg Gazef to stand up. Ainz informed them that their friend was dead. As Brain and Climb head toward Gazef's body and grieve over him, Ainz eased their pain by telling them that the man died like a true warrior and because of his act of heroism, he decided not to continue the pursuit in honor of him. Ainz was ready to prepare a proper burial for him but Brain politely declines, saying that he and Climb will make sure to take care of it. The Sorcerer King accepted but informed the two that a high-tier resurrection spell was required to revive Gazef, a spell which they and the entirety of the New World do not possess. As he left the battlefield, the Sorcerer King made one final warning: E-Rantel must be offered to him or he will command his Dark Young to ravage their kingdom. The battle over, Brain decided to carry Gazef's body while Climb took care of his belongings.
The battle was over with the Empire and Ainz Ooal Gown claiming victory.
Many men from the Royalist Faction, Noble Faction, soldiers and conscripts lost their lives. 70,000 had been killed by the super-tier magic and following that, another 100,000 was added due to the Dark Young totalling up to at least 170,000 killed.
The King and the survivors managed to return to E-Rantel but not without suffering major wounds. Their soldiers were severely injured or traumatized by what they had experienced. Families are left orphaned and widowed due to the deaths of their fathers and husbands. Since many nobles including the first sons had been killed, the second heirs or any reserves were to take over their late relatives' former positions. King Ramposa had been informed about Gazef and is struck with intense sadness over the loss of his friend. With Prince Barbro having yet to return from his mission, Adventurers were hired to find him.
The King and his court reached a unanimous decision and that is to immediately relinquish E-Rantel to Ainz Ooal Gown, in an effort to save the Re-Estize Kingdom.
Marquis Raeven abandoned the Re-Estize Kingdom deciding that it was a lost cause. He returned to his home and stayed there to be with his family.
Brain and Climb met up at the tower Gazef brought them to. The two discuss what had just happened and lament over Gazef's death. Eventually, they came to agree that their friend provided them another chance and they should not waste it. Climb continued to protect Princess Renner while Brain vowed to Gazef that he will one day surpass him.
Reports came back to the Baharuth Empire. Jircniv was horrified by what he had learned. He had severely underestimated Ainz Ooal Gown and now his plans had produced the opposite results. Ainz's spell had single-handedly crippled an entire kingdom to ruin and the news will spread throughout the other neighboring countries who will be highly reluctant or too frightened to stand against the Sorcerer King. The Empire was now on their own and the Emperor grew paranoid, fearing what the monstrous entity would do to him and his nation should he learn of their deception.
Unknown to all participants of the event, the Slane Theocracy had a minor involvement. They had one of their agents sent there to learn more about the Sorcerer King and discover any secrets they could use to counter against him. It proved futile as the agent returned, unable to talk after having been scarred from what she had seen.
Some time passed, the now abandoned E-Rantel was left defenseless allowing the forces of Nazarick led by Albedo to enter the city, unopposed. A parade was held there to commemorate Ainz's victory but none of E-Rantel's citizens appeared before him, scared of their new ruler. Then, a boy exited out of his house and attempted to throw a rock at Ainz but only able to hit the Death Knight. He demanded Ainz to give him back his father and called the Sorcerer King a monster. The boy's mother stepped in to protect her son and begged Ainz and his army for forgiveness. Albedo refused to ignore what that boy had done and she declared that he must be punished with death.
Suddenly, help came in the form of Momon who defended the mother and child from Albedo. The two exchanged hateful words to one another before preparing to fight to the death. That is until Ainz Ooal Gown came and calmed Albedo down to inform her about something. Albedo smiled and turned to Momon. She informed that her king has a proposal for him. If the Adamantite ranked Adventurer swore loyalty to the Sorcerer King, then all the lives of E-Rantel will be spared from retribution but if he refused, the battle will continue and collateral damage and casualties will be high. Momon accepted those offers, having left with no other options.
Truthfully, this was all part of the Sorcerer Kingdom's machinations. Demiurge had hypnotized the boy to commit the act forcing the Raven Black Hero to intervene and be forced into servitude. The boy's condition will be blamed on the Slane Theocracy, ensuring the nation will be discredited and preventing anyone in E-Rantel from asking for their aid. Momon (an identity worn by Ainz Ooal Gown and Pandora's Actor) will stay and calm the citizens from revolting and spy on anyone who dared to do it. With that, the Sorcerer Kingdom was established and it has become a land of peace.