During a mission undertaken by Shalltear Bloodfallen, the Floor Guardian caused a disturbance, annihilating an iron ranked adventurer team. One of the adventurers managed to slip away and escape back to E-Rantel. The Guildmaster Pluton Ainzach learned from the survivor that the team had faced a powerful vampire with abnormal abilities. Usually, a platinum ranked adventurer would suffice to eliminate the monster, but given the circumstances, Pluton decided the best course of action would be to summon all mithril ranked adventurers and handle the situation from there.
Ainz Ooal Gown upon learning that a Shalltear had rebelled against Nazarick, quickly teleported back to the Great Tomb of Nazarick. Reuniting with Albedo they use the dungeon's administration system and determine that Shalltear is indeed under the control of an outside influence. In order to find Shalltear, he and Albedo go to the Frozen Prison on the 5th Floor to visit Nigredo and use her magic to locate her.
Through Nigredo's magic, the pair discover that Shalltear is maintaining her position but is now fully equipped in her Bloody Valkyrie form. Soon after before they could commit any action, Ainz then learns from Narberal Gamma that the Adventurer's Guild in E-Rantel is looking for him concerning a vampire. Resuming his identity as Momon, and goes to the Adventurer's Guild meeting. The meeting had summoned several other mithril adventurer teams: Darkness, Rainbow, Sky Wolf, and Kralgra. The plan was to have the adventurers combine their forces to defeat the vampire. Knowing this would be detrimental should his connection with Shalltear be discovered, Momon interjects stating that they would all die.
Momon insists to the Guild leaders, E-Rantel's authorities and his fellow Mythril adventurers that he will exterminate the vampire. He concocts a story that tells him he is familiar with the vampire, as he has been hunting her, Honyopenyoko, and another vampire. All of the people in the room are aware of Momon's reputation but are doubtful that he alone could defeat the vampire.
Their concerns are washed away when Momon reveals his trump card: a Sealing Crystal containing a seventh tier level spell. Momon insists that Darkness will fight against Honyopenyoko alone, arguing that involving others in the fight will simply increase the number of casualties. Nearly all in the room acquiesce to his terms save Igvarge of Kralgra, who demands his group accompany Momon in the fight against the vampire, which the latter accepts. En route to the destination where Shalltear is located, Ainz has Kralgra ambushed, intending to silence them and blame their deaths on Honyopenyoko. Igvarge manages to slip away but soon is restrained and killed by Mare Bello Fiore. Witnesses being taken care of, Ainz introduces Hamsuke to Albedo and orders Narberal to escort the hamster to Nazarick so it may be acclimated with the members of the tomb.
Albedo and Ainz head towards Shalltear. Just as Nigredo magic shown she was indeed on standby possibly due to an incomplete mind control magic. Despite having countermeasures against mind=control the vampire has fallen under an influence of at least as strong as a Divine Item. To undo the spell on Shalltear, Ainz reveals his wish-granting magic ring, Shooting Star. To his shock, the magic fails. Ainz frantically orders a retreat, teleporting himself and Albedo to a safer location. Before Albedo asks what is wrong, however, Ainz goes through a tantrum of rage kicking the dirt in anger. When his undead racial effect kicks in, the Overlord calms down and tells Albedo the magic of a Divine Item didn't have any effect on the mind control placed on Shalltear. In that effect, it could only mean one thing that Shalltear was affected by a level greater than it: World Items. Ainz fear is justified as they are an object of power that could change the balance of power. He didn't anticipate any World Items to exist in the New World. The potential danger of the World Items brought to light, Ainz first orders Albedo to recall all Floor Guardians outside of Nazarick to verify if they are comprised and to escort him to the Treasury.
At the entrance to the Treasury, Albedo and Ainz are joined by Yuri Alpha and CZ2I28 Delta. Before the entrance, Ainz opens it using the universal password. Passing numberless artifacts and weapons they reach the inner sanctum where the group encounters a strange octopus humanoid. Albedo recognizes it as her creator Tabula Smaragdina. However, upon further scrutiny she quickly sees it as an impostor, causing Yuri and Shizu to prepare for battle. Ainz orders them to stand down and reveals that the impostor is really a Doppelgänger named Pandora's Actor, the Area Guardian of the Treasury. The Area Guardian resuming his natural form dramatically introduces himself and offers his services. Seeing that his master has come to the Treasury, the Area Guardian deduces that he has come for the World Items and that there is a situation that may threaten Nazarick. While painfully listening to his creation's antics, Ainz pulls Pandora's Actor aside and tries to impress him to act seriously which the NPC reluctantly agrees to try. Before going into the Mausoleum to retrieve several artifacts, Pandora's Actor requests to be allowed to leave the Treasury to better serve Nazarick with more efficiency. Though hesitant to move a being such as Pandora's Actor to the other floors, he relents and gives him a Ring of Ainz Ooal Gown, ordering him to keep to the 10th Floor. After that, he orders Albedo to give her Ring of Ainz Ooal Gown to Pandora's Actor and follow him to the Mausoleum.
Inside the Mausoleum, Ainz shows Albedo the Avatara, golem statues made into the likeness of each of the Supreme Beings to serve as a memorial to his comrades and to safely store away their divine gear. He tells Albedo once a day a statue of him will be here. Albedo takes it that Ainz means to leave them and begs him to stay with Nazarick forever. Ainz cannot promise her that and tells her that should he be gone leading Nazarick and the other Floor Guardians will fall to her. He tells her his intent to face Shalltear alone, despite her protests, stating it is his responsibility and he does not wish for his children to kill one another. Albedo seeing his determination, demands that he promise her one thing, to come back.
Returning to Shalltear's location, Ainz Ooal Gown escorted by Aura Bella Fiora and Mare Bello Fiore orders them to monitor the area for interlopers. Separating from them he prepares to engage Shalltear.
Meanwhile, Demiurge who has returned to the Great Tomb of Nazarick, meets with Cocytus and Albedo. He to know the current situation. Upon learning that Ainz intends to face Shalltear Bloodfallen alone Demiurge insists that they should not be allowing this. Despite Albedo's confidence that Ainz will be victorious, he criticizes her acceptance of Ainz's decision. Demiurge attempts to leave to assist his master but is stopped by Cocytus who is under orders from Ainz to prevent any interference. Faced with fighting a comrade, Demiurge relents, however, he warns Albedo that should Ainz perish Albedo must step down as Overseer Guardian. Albedo accepts, maintaining her belief that Ainz will return to them.
Approaching Shalltear, the Overlord sees that she is still in her standby mode. Ainz then prepares for battle, buffing his stats with several spells and arming himself with Quick-Change Items. He casts the Super Tier Magic: Fallen Down which causes massive damage, creating in a gigantic crater where the Floor Guardian stood. Shalltear who been in a stationary position goes on the offensive with her Spuit Lance. Being relatively unharmed, Shalltear prepares to attack her former master.
Aiming the tip of the lance at Ainz the former remains unmoved and counters with [Triple Maximize Magic: Explosive Land Mine], blowing her away. He continues the assault casting [Maximize Magic: Gravity Maelstrom] at her flying body. Shalltear manages to stabilize herself and casts [Wall of Stone] to shield herself from the spell. The attack is followed up with [Maximize Magic: Hold of Ribs] to restrain her in a skeletal cage but she shrugs it off easily. Ainz takes the moment to inform Shalltear that he set mines around the area and suggests attacking him from the air, making the vampire think he has traps in the air. In truth Ainz only had ground mines but with this bluff, it will restrict Shalltear's movements.
Bracing Spuit Lance in anticipation Shalltear uses [Mana Essence] to gauge his mana reserves and is surprised at its high level. Finding a greater appreciation towards her opponent, worthy as a Supreme Being, Shalltear prepares herself and casts [Regeneration] to heal herself. Ainz then launches another [Maximize Magic: Gravity Maelstrom]. Rather than caste [Wall of Stone], Shalltear used [Greater Teleportation] to teleport herself into close range and begin melee combat. When she casted the spell she felt slow and realized Ainz had countered and used [Delay Teleportation]. Still, quite a distance away from her target, she sees three sparkling balls of light, [Drifting Master Mine]s. Before they could touch her she turns into her mist form to avoid, only for Ainz to call her for being naive as he activates [Maximize Magic: Astral Smite], a spell effective against astral entities such as Shalltear in her mist form.
Shalltear is assaulted by the spell and wracked in pain as she is forced out of her mist form. Impressed Shalltear praises her former master. Noting that his mana levels had gone down, Shalltear casts [Force Sanctuary], a defensive barrier, to impede his movement and negate his attacks. Ainz sensing that he would not have much time before the spell fully takes into effect, scrambles to cast a spell. Shalltear is confident in her victory though she wonders why Ainz is not using any additional items to aid himself. Ainz manages to cast [Maximize Magic: Thousand Bone Lance] causing countless lances of bones to erupt from the ground around him and assail the barrier until it breaks and dispels. Ainz then follows up with another spell, before Shalltear teleports to a location outside his [Delay Teleportation]. Ainz readies a [Maximize Magic: Gravity Maelstrom]. Shalltear though calm and collected is fascinated by Ainz's prowess and continues to praise him despite needing to kill him.
Confident she unleashes [Impure Shockwave Shield], an offensive and defensive skill that summoned a red-black wave of blood that disintegrates the incoming gravity attack. Ainz is taken aback by the skill, drawing humor from Shalltear who then proceeds to show off another skill. She conjures a [Purifying Javelin] and directs it at Ainz. The lance hits Ainz in the chest and with its holy-element damages him. The attack is soon followed by another lance and pierces Ainz's shoulder.
Seeing that she is looking down at him, Ainz activates [Maximize Magic: Reality Slash] a 10th tier spell that cleaves through space and slashes at the vampire's chest. Unfortunately, the damage dealt healed itself leaving her unharmed as a result of another of Shalltear's skills. Laughing at her master, as two exchanged attacks, Shalltear wonders why she is attacking him but cannot fathom the reason only the need to kill the enemy. Through her [Mana Essence] Shalltear is pleased that Ainz's previous attack has drained him of mana while she, on the other hand, has recovered her mana reserves. Curiously Ainz continues to use [Reality Slash], a most inefficient way given its mana consumption and damage power. Still, the vampire was confident that her skills could allow her to adapt to whatever Ainz threw at her. After trading a [Purifying Javelin] with a [Reality Slash] from Ainz, Shalltear attempts to drag out the battle by summoning more minions casting [Summon Monster 10th], only for Ainz to negate it with [Greater Rejection].
Undeterred Shalltear unleashes [Maximize Magic: Vermilion Nova], a crimson flame engulfs Ainz. Before it can take him Ainz counters with [Triple Maximize Magic: Call Greater Thunder] which the lighting strokes shock Shalltear's body dropping her health significantly. Raising his fire resistance Ainz endures the attack cast by Shalltear. The two then begin trading spells on each other, Shalltear casts [Maximize Magic: Brilliant Radiance] whereas Ainz casts [Maximize Magic: True Dark]. Both endure the attacks, though Shalltear sees Ainz wavering to her delight. They exchanged magic in a back-and-forth fashion for a time both losing a sizable amount of health.
Despite being weakened by the exchange, Ainz was still very much determined pleasing Shalltear as it would give her greater pleasure at breaking him. Using [Maximize Magic: Greater Lethal] Shalltear channels negative energy into herself to heal. Determining that one spell wasn't enough to restore her Shalltear begins another spell only to stop when she sees that Ainz's wounds are also healing. Initially mistaking it for a spell, Ainz corrects Shalltear explaining it to be the effect of a magic item that allows him to use [Greater Lethal] even if it is not in his spell list. Shalltear casts several [Greater Lethal]s on herself to recover while Ainz casts the defensive spell [Body of Effulgent Beryl].
Knowing that she will have to launch a direct attack, Shalltear brandishes her Spuit Lance. Annoyed that it was a disadvantageous fight Shalltear claws at the question of why she is fighting Ainz. Ainz apologizes to her for being stubborn but states that he will not run as it is for the sake of the guild.
Starting again Shalltear unfurls a pair of giant bat wings and several Elder Vampire Bats emerge from her back. Ainz summons a tornado through [Sharks Cyclone] engulfing the summoned creatures. Despite the conjured sharks in the maelstrom Shalltear crosses through and thrusts her lance at top speed. Not able to react in time Ainz the weapon stabs through him. Briefly feeling agonizing pain, Ainz's nearly loses consciousness but maintains his mind through sheer will. Activating [Body of Effulgent Beryl], the spell absorbs the damage dealt by the lance, making time seem to go backward. Ainz's body is moved back to where he had been standing before the lance had pierced him.
Shalltear baffled by the display, Ainz then casts [Wall of Skeleton] creating a barrier between the two of them. The skeletons in the wall all attempt to attack Shalltear but she comes out unscathed. Soon Ainz casts [Maximize Magic: Force Explosion] creating a shock wave explosion that destroys the wall with Shalltear in the vicinity. Buying him some time he follows with an attack [Triple Magic: Greater Magic Seal], triggering three magic circles releasing 90 [Magic Arrows] hitting their mark. Continuing the Overlord casts [Dance] and [Triple Magic: Obsidian Sword] making three long swords appear in mid-air and attack Shalltear.
Annoyed by the attacks Shalltear paid no heed to them and pressed onward toward Ainz. Ainz is sent flying by Spuit Lance to the side but he stabilizes himself in the air using [Fly]. Weathering the attack Ainz begins to grow frustrated as Shalltear had sapped his health to replenish her via the attack. He casts [Triple Maximize Magic: Reality Slash], dealing wounds on Shalltear but she pays it no heed and advances. Knowing that Shalltear was depleted of mana and her only option was to press on, Ainz retreats via [Fly] and casts his previous spell again. Even with the damage, she continues to approach him before curling herself and causing a [Fire Explosion]. The shock wave sends the Overlord flying, before tumbling along the ground. By his magic items and [Fly] spell he manages to get back up. The distance between them lengthen allowing Ainz to casts his spells. Before he could do so Shalltear summons her Einherjar as her trump card. In addition, she summons countless minions and proceeds to pierce them with her weapon in order to restore her health.
The Einherjar then charges at him knocking Ainz back. At that point, Ainz uses his own trump, his Eclipse class combined with his skill [The Goal of All Life is Death]. Simultaneously he casts [Widen Magic: Cry of the Banshee]. The wail though having an instant death effect was useless against Shalltear and the Einherjar, but the summoned minions were affected and ceased to exist. Despite the continuing barrage of attacks on him by the high tier summon, twelve seconds pass and his spell take effect. The world around them died, the Einherjar evaporated as well as Shalltear's remaining summons. The magic affects a 100-meter area in all directions turning the area to sand. The only ones standing were Ainz and Shalltear, who used a resurrection spell to resist it. Ainz is surprised by the effect of his spell on his surroundings as this would have never have happened in YGGDRASIL. Swallowing his surprise he focused at the task at hand, maintaining his control of the situation acting that this had been part of his plan.
Engaging Shalltear in a conversation, he asks his former servant what she thought of experiencing his power. Shalltear admits that she is impressed and expected nothing less of him. Though her summons are dead she boasts that his mana has been almost depleted whilst her health is at maximum. Ainz notes that she herself can at least perform two more 10th tier spells which she confirms. Her victory close at hand Shalltear tells her master not to be saddened as it was commendable for him to be able to last as long against her. When Ainz humbly states that he accepts her praise she becomes annoyed at his nonchalance but pushing her pride aside and begins to close the distance between them to deliver the final blow. She asks is he has any last words only for Ainz to chuckle stating though he is at a disadvantage things couldn't have gone as according to plan. Going to explain his actions of attacks and her counters. Even though she understood little of his rhetoric, his confidence throws her off and causes the Floor Guardian to think that Ainz planned everything from the beginning. Though she tries to convince herself that everything is just a bluff and continues on her path. It was only until she heard that Peroroncino had told Ainz about her specifications does become uneasy. Agitated she strikes him only to have Ainz's timed spell activate. Spuit Lance is repelled as Ainz is soon engulfed in white radiance.
The light dims and Ainz Ooal Gown appears wearing a suit of white armor. Ainz proudly states he has long since been preparing to fight the vampire in a melee battle. The Floor Guardians watching from afar recognize it to be Touch Me's personal armor. Normally a World Champion would only be granted the right to don it, however thanks to Ainz's use of [Perfect Warrior] he can bypass the limitation and access its abilities. Shalltear is struck by a cleave of Ainz's lightning infused blade, which is a katana known as Takemikazuchi MK 8, once wielded by Warrior Takemikazuchi. Shocked at the weapon, Ainz tells her the name of Ainz Ooal Gown is invincible and she is fighting its incarnation of the forty-one Supreme Beings. Advancing Ainz slashing another attack which Shalltear avoids, and attempts to jump forward to attack. Going by his warrior instincts, the Ainz's blade is then shifted the point of the blade to halt Shalltear's attack. Seeing it Shalltear decides to take the attack, putting her hand in the weapon's path. Her palm impaled she diverts it to one side. Ainz now open for an attack, lets go of the weapon and takes out a series of sticks. Using them he summons twin kodachi, which though causes Ainz some damage in his hands, are effective in dealing Shalltear pain as well. Soon enough just as Ainz blocks a counter move by Spuit Lance, he unleashes a throw of a giant gauntlet, flinging her backwards. Regaining her balance she soon is targeted by an elemental damaging shot from a golden bow.
Now running out of mana and skills, Shalltear finds her defenses waning. The Floor Guardian recognizing the last weapon to have belonged to her creator demands to known how Ainz obtained it as well as all the other weapons he just used. Ainz refrains to divulge her the secret to his tricks, though states that throughout this battle everything has been playing out as he planned. Retreating a pointless endeavor Shalltear pressed her attack but the white armor Ainz wore had high defensive power. Despite this Shalltear was confident that it could not be unscathed by her Spuit Lance. Ainz then raised a blood red axe causing her to pause before continued her fight. Both attackers now exchanged blows eating at each other's health. Throwing herself wholeheartedly into her attacks Shalltear believed that she could still win. However, she suddenly hears a vaguely familiar voice, "Time's up—Momonga-oniichan!" which emitted from Ainz's wristwatch. Ainz seeing that it was time, dismissed his weapon and replaced it with a shield and uses it to block Shalltear's blows. The Overlord continues to say that the battle is over and victory is his. The vampire is further confused by these boasts, but Ainz iterates that Super-Tier magic may not be able to kill her at full health in one hit. But if he reduces her health enough then that immunity is moot.
Knowing defeat to be at hand, Shalltear continued to her frenzied attack pattern, but each blow is easily countered by Ainz. Given that he needed to cast Super-Tier Magic, Ainz needed to cast off [Perfect Warrior], at the cost of being left vulnerable. Knowing the risks he proceeded with the plan, taking out an hourglass to hasten the Super-Tier spell. Just as Shalltear was about to land a spear attack on her master, she found only empty air. By the time she reoriented herself, Ainz had smashed the cash item in his hand reducing the Super-Tier Magic cast time to zero. The Super-Tier spell, [Fallen Down] is activated and a huge pillar of blue light from the sky turns the whole world white. The effect on Shalltear is, and her right arm is carbonized causing her to drop her weapon, followed by being shriveled up from the heat of the spell. Seeing that she has lost Shalltear expresses pride to Ainz. Before she vanishes into oblivion she notes that her lapse in awareness that allowed victory possible was a form of mental effect that was possessed one certain person: Aura.
Aura having used her skill to allow Ainz Ooal Gown victory over Shalltear opts to keep it as a secret from not only her master, but also to her fellow Floor Guardians to maintain his invincible appearance. Ainz after reclaiming Shalltear's equipment returns to Nazarick in the Throne Room where his return is celebrated by the gathered Floor Guardians. Before Ainz begins the process to resurrect Shalltear Bloodfallen, the other Floor Guardians insist that he allow them to protect him should Shalltear shows any sign of betrayal. Using the 500 million gold coins from the Treasury, Ainz brings the fallen Floor Guardian back to life. The gold coalesces into the naked form Shalltear. Albedo is wary of Shalltear but Ainz observes that the vampire is no longer under the influence of mind control. For her body, Ainz conjures a cape to cover her. Shalltear soon awakens confused at her surrounding is soon greeted by an embrace from her master. Ainz apologizes to her servant for the experience he put her through. The vampire exhausted tries to make sense of the situation, Ainz questions her on her last memory. However, the last recollection Shalltear possessed was from five days ago before she had set off from Nazarick and into the New World. She could not give any explanation of what had transpired. Ainz now very unsure of his power given that there existed entities that could hurt his 'children', vows to avenge himself against whoever was responsible. Albedo eager to assist her master suggests they acquire assets to strengthen Nazarick and like the lizardmen of the Great Lake area.
The news of Momon defeating the vampire, Honyopenyoko, gains him and Nabe fame. This feat advances the two into mythril ranking adventurers. Meanwhile, the Six Cardinals after the Black Scripture had reported the unknown vampire had given orders for the area where the vampire to be monitored. They initially believed that only a God-Kin or Dragon Lord would be a match of the undead. However should such as entity appear and defeat the vampire, the held that being would be someone they had to be wary of appeared, and they would tighten their national defense first in response to the potential threat.