Every year, the annual war between the Kingdom and the Empire seems to be nearing its end. However, the ruler of the Empire, Jircniv, also known as the "Bloody Emperor", visits the Great Tomb of Nazarick and allies with Ainz Ooal Gown, which drags him between the conflict of the two nations, changing it into a total war.
Notice: The beginning of Volume 9 is the continuation of where Volume 7 left off.
After the two dark elves killed off more than 100 elite guards within the Imperial Garden, Emperor of the Baharuth Empire, Jircniv Rune Farlord El Nix greets both of them who're Nazarick's envoys to the palace. The casualties include one of the Four Imperial Knights - Nazami Enec. While attempting to prolong the negotiation, Jircniv tries to extract information out of the two dark elves. However, the attempt ended in failure due to the latter, where Aura threaten to destroy the Empire if he doesn't apologize to Ainz Ooal Gown immediately.
Later on, Jircniv along with Fluder Paradyne accompanied by twenty elites guards, traveled to the newly built tomb that Aura constructed with the original purpose of warehousing. On their way to Nazarick, he discussed something about resurrection magic with Fluder and finds out that while fifth tier resurrection magic makes the revived lose vitality (meaning level drop), the Dragon Queen of Dragonic Kingdom's Wild Magic is able to cast revival without the side effect of the vitality loss. The discussion ends with Fluder stating that Wild Magic is a completely different branch of magic so there is no way to confirm this theory.
Upon arrival, he is astonished at the beauty possessed by the battle maids and the wealth of Nazarick. When they saw five Death Knights appearing and forming a line, Fluder immediately screams and causes the others to become frantic. Even Jircniv's strongest guard, Baziwood Peshmel, cannot help but tremble at the terrifying atmosphere emitting from these Death Knights. Through learning the Death Knight's strength and Yuri's confirmation that Ainz has absolute control over them, Jircniv now realizes that he's meeting with a powerful magic caster while Fluder on the other hand, laughs facing the sky. Astonishingly, Jircniv is even more surprised when he bore witness to many different races gathered in the throne room: dragons, demons, insects, demi-humans, etc. while all of them seemingly possess significant power. He is actually less surprised seeing Ainz as an undead, since imagining a human ruling over such a variety of monster would be strange. After apologizing and blaming everything on Count Femel whose head he brought along, Ainz then turns Femel's corpse into a Death Knight right on the spot. This causes the envoys to feel terrified as he just created a Legendary Undead in front of them with apparent ease. Jircniv proposes an alliance with Ainz and Nazarick, in which he agrees.
Leaving with mixed feelings, Jircniv calmly assesses the situation in the carriage and suspects that Fluder has betrayed him. He silently seeks to recruit potentially powerful magic casters in the event that he will need to replace Fluder, at the same time, seeking to form a grand coalition with Re-Estize Kingdom and Slane Theocracy against Ainz. He also wants to gain an insider spy in Nazarick after seeing so many races in there, as Jircniv thinks that there should be at least one creature discontented with his or her position whom would be willing to leak some information and cause a revolt inside Nazarick.
Meanwhile, Ainz and the Guardians already saw through Jircniv's scheme of betraying them thanks to Demiurge's insight, laughing at how shallow-minded the emperor is. Shalltear suggests to turn him into a vampire. However, Ainz, favoring Demiurge's idea, had a better idea. If Jircniv's intention was to form an alliance with other countries to battle against Ainz Ooal Gown, then Ainz himself just needed to demonstrate to all the consequences of any whom dares to oppose him and Nazarick itself.
A month later, King Ramposa III, along with the royalties and the six great nobles gathered for a meeting as they just received a declaration from the Empire that they are forming an alliance with Sorcerer King Ainz Ooal Gown's country. More so, declaring war for Re-Estize Kingdom's unrightful rule over the territory of E-Rantel, that should be return to its rightful ruler. This causes everyone to be in a heated debate over this mad declaration. Eventually, they simply dismiss it as another mere excuse for the Empire's annual war, laughing at Ainz as just some foolish joke. However, feeling uneasy, Gazef Stronoff warned the nobles not to underestimate Ainz. In the end, the Kingdom still decided to accept the declaration of war.
Two months later in the winter, an army of two hundred and fifty thousand soldiers were situated at E-Rantel. The royalties and top nobles gathered together are discussing about their war preparation plans against the Empire's forces. Everyone was shocked at the report that the Empire gathered sixty thousand soldiers, which is three times more than the typical amount of the past wars, and they also received an announcement from Slane Theocracy declaring their neutrality. The news causes the nobles to suspect the countries wariness as they were all making such an overreaction over a single magic caster. Due to the nobles' ignorance about magic, they believed that magic casters were just performers, who used tricks such as fire balls and flight in the battlefield. They believed that a single magic spell that could cause great destruction is just a myth. After Gazef's constant warning and persuasion not to underestimate Ainz, they decided to send five thousand men to fight Ainz as an estimation of his power in the war, but Gazef still thinks that they are underestimating him. Afterwards, the King ordered Prince Barbro to travel to Carne Village with an army of five thousand to collect information on Ainz while Marquis Raeven was given total command over the army in Katze Plains.
After the meeting, Gazef is still in deep thoughts, thinking that it is a grave mistake to fight Ainz in the first place. He then meets up with Brain and Climb, asking them to have a chat with him somewhere in private. After chatting and enjoying the view of the plains, Gazef warns Brain that he will never be able to win against Ainz. Then, Brain also talks about Momon's fight against a strong vampire who appeared, that could be related to Shalltear Bloodfallen, and wanted to investigate further.
At the Empire's Imperial Castrum, Nimble Arc Dale Anoch meets up with the army commander. They talk about this war being a bloody battle to capture E-Rantel as a gift to honor the alliance between the Empire and Ainz Ooal Gown, while building a friendly relationship. The empire also request for Ainz to cast one of his powerful magic, to determine his power. They then welcome the Sorcerer King's arrival with great hospitality. Afterwards, Ainz's army is teleported and their arrival made everyone realize, with just their appearance alone, that the small army of five hundred is not to be underestimated.
While marching towards Carne Village, the first prince is angry at the king for not allowing him to join the war at Katze Plains. Thinking of his siblings and fearing that he was cast away with the throne being decided by the king already, he then decides to make an outstanding achievement. He concludes that he would make the villagers there join his army, and return to the war at Katze Plains.
Later, Enri Emmot was alerted of the Kingdom's army marching towards their village. Then the prince's army's messenger answers to Enri's questioning about Kingdom being at war with Ainz and demanded the villagers to open the fort gates for further investigation. The villagers immediately accept that if it is about their savior, then the Kingdom must be the ones at fault. Due to their gratitude to Ainz and also not wanting to expose the goblins and ogres in the village, Enri still persist on not opening the gates. As the first prince becomes impatient and angry at Enri's persistence, he orders the archers to launch fire arrows at the village as a warning. The villagers still not wanting to betray Ainz while at the same time angered by the fire arrows, did not hesitate to fight against the army, resolving to die.
While the goblins, ogres and male villagers stay to fight, they planned to lure the enemy army into the village to attack the enemies flooding in first and then distract the ones outside by thinning their numbers through causing the enemy army to spread around the surrounding outside of the fort. During the fight, Enri would escape behind the fort to the forest with the rest of the villagers. However, all of this failed when Enri's group escaping to the forest were chased by the Kingdom's soldiers riding on warhorses. Out of desperation, at the same time desiring to protect the helpless villagers and Nfirea, who were preparing to stall the soldiers, Enri blows her second Horn of the Goblin General.
While the dying goblins and villagers made their final effort to fight back, they stopped upon seeing the sudden appearance of an army of goblins. This causes them to retreat back into the ally goblin's army. While the first prince felt angry at himself being forced to fight some lowly goblins, ordered his army to continue fighting instead of retreating but was overwhelmed by the goblin's army easily, forcing the first prince to retreat. After managing to escape safety at the plains, Lupusregina Beta suddenly appears behind them, claiming to have observed the situation before and she also been sent to kill everyone under Ainz's orders. She then summons thirty level 43 redcaps goblins, killing everyone with only the first prince dying after half an hour of torture by Lupusregina.
At the Katze Plains, the Kingdom and Empire's armies are stationed facing each other. Many of the nobles still predict that their losses would be minimal even if Ainz entered the war, but this time the Empire's army did not make the first move. As time passes, anxiety and tension rises among the Kingdom's ranks as both armies on each side remains in stalemate. Thinking that the Empire's army was waiting for something, Marquis Raeven then starts a discussion with Gazef, whom was fully equipped with the Kingdom's treasures. But even so, Gazef still thinks that he can't win against Ainz. At that moment, the Empire's army started to separate into two flanks, effectively opening a path for an army bearing an unknown banner, consisting of two hundred Death Knights, with the rest of the other three hundred armed troops having an unusual appearance, making the army five hundred in total. Marquis Raeven's adventurer bodyguards warned him that the five hundred mounts that the unknown army are riding are the legendary Soul Eaters that could killed hundred of thousands of people in the past with just three. Hearing this, Marquis Raeven immediately ordered the army to retreat. However, Ainz at the front of the army with Mare and Anoch standing at his sides, started casting a single bright spell.
As Ainz cast his super-tier magic, Iä Shub-Niggurath, a dark vortex flows towards the direction of the Kingdom's army, instantly taking the lives of seventy thousand soldiers from the Kingdom army's left flanks. As confusion arises amongst the rank of the Kingdom's army, the Empire's army witness and realized the horror of what just took place, was being even more terrified at Ainz's calmness of the situation. Ainz then told the pale Anoch that his magic has not ended just yet.
A giant black blob descended from the void in the sky covering the corpses of the dead soldiers like a wave of darkness. Then five Dark Young are summoned, with levels higher than 90, started growing and forming from the darkness. Ainz laughs at this situation as he just broke the game world record of being able to summon five of such monsters. Mare and Anoch then congratulated Ainz, while everyone else were trembling uncontrollably. Ainz then orders the Dark Young to attack while telling them to spare four specific people. The massacre began as the Dark Young started rushing towards the army. The Dark Youngs bulldoze through the army's flank. Screams and cries were everywhere, One of the Dark Young then started chasing Marquis Raeven and his adventurers. It killed all of Marquis Raeven's adventurer guards instantly, but it suddenly stopped in front of him.
During that moment, Ainz then takes off his mask and called upon the Imperial Army to cheer for his supreme power. They desperately cheered loudly for him in order to avoid the same fate as what had just happen with the Kingdom's Army. One of the Dark Young was returning to Ainz and headed toward the Imperial Army's direction, caused every single one of the imperial soldiers to run for their lives, trampling over their own allies. The Dark Young placed Ainz on top of its head and Ainz thought after casting his most powerful spell, the Imperial Army would charge in but seeing the carnage it was understandable that the Dark Young did all the work. Ainz then decided to continue his assault while Mare was left in charge with his army and its seem he finally found his main target. Abandoning the horses, Gazef's warriors carry their king in full retreat back to E-Rantel while the Vice Captain, Climb and Brain Unglaus became decoy to distract the Dark Young and buy some time for the King to escape.
In the meantime, Gazef himself was trying to stop the Dark Young in the frontline but was ignored by it. Yet another Dark Young appears with Ainz sitting on top of it came to greet Gazef with Climb and Brain arriving there too. Ainz then ask Gazef to join him in exchange for stopping this war. However, Gazef has chosen to decline his offer, and instead he challenged Ainz to a duel. Ainz accepted his challenge, and asked the two other people to be the witness of their match. Immediately after the battle starts at Climb's signal, Ainz stopped time around them using Delay Magic along with True Death to kill Gazef instantly, without him being able to even react. Afterwards, Ainz tells Climb and Brain that he will stop the attack but demands them to give away the territory around E-Rantel. Ainz then returned to the Empire's fortress with all of his monsters. Afterwards, Brain made a declaration to Climb back in E-Rantel that he is going to continue Gazef's legacy.
Later in spring, rumors were being spread about a horrifying new ruler in E-Rantel. As E-Rantel became a part of the Sorcerer Kingdom. Ainz, Albedo and his army of death knights and death warriors enters E-Rantel. Albedo then decides to kill a young boy, who is disturbing their arrival march but was stopped by Momon. Albedo threatened Momon and tells him to serve Ainz as the city's enforcer, which he accepts. After Ainz's army left, Momon then asks the residents not to start a rebellion and be careful of instigators for his sake. Afterwards, E-Rantel became a peaceful city without bloodshed under the rule of Ainz Ooal Gown.
- Chapter 1: A War of Words
- Chapter 2: Preparations for the Battle
- Chapter 3: Another Battle
- Chapter 4: Massacre
- Brand New Chapter
- Jircniv commented that Nazarick should be called "The Devil City" as many horrible monsters exist there.
- Ainz Ooal Gown named himself the Sorcerer King after Cocytus's suggestion.
- Overlord Volume 9 was released a week before Season 1 of Overlord anime adaptation started airing.
- Fluder Paradyne quits his position immediately after encountering Ainz to become his disciple.
- The Kingdom sends 1,000 men to capture Enri, they were killed by 30 Redcap Goblins.
- Since Mare doesn't exist, Fluder Paradyne is with Ainz during the massacre at the Katze Plains.
- The Death Knights ride on Skeletal Dragons instead of the Soul Eaters.
- Gazef Stronoff survived the massacre while Marquis Reaven was trampled by the Dark Young.
- Since Ainz doesn't establish a nation, E-Rantel became part of the Baharuth Empire.