The plan was proposed by Demiurge who believed that tricking the Baharuth Empire into sending workers to invade Nazarick. Though the invasion, in terms of practicality, would use the invaders to test the effectiveness of the dungeon defense systems, it would also be the best plan of action as the first step in Ainz Ooal Gown's conquest of the New World.
The plan itself had three initial goals: First was to force the surrounding nations to acknowledge the existence and power of Ainz Ooal Gown. Second, the cost, both monetarily and in missed opportunities, from being forced to hide in the shadows would be relieved due to Nazarick's public announcement. And finally, there was the issue of the attackers who brainwashed Shalltear still roaming about. With the newly gained freedom of movement, Nazarick would no longer be forced into the shadows and gain the cooperation of the neighboring kingdoms, hunting the transgressors down would be much easier.
Momon and Nabe entered Arwintar and summoned Fluder Paradyne to a private meeting. Taking advantage of his lust for more magical knowledge, both Ainz and Narberal showed him their true magical power, upon which, Fluder begged to be made Ainz's student, offering everything he had in return. Ainz took this opportunity to set Demiurge's plan in action by having Fluder suggest sending workers to Emperor Jircniv Rune Farlord El Nix in order to find out more about the mysterious magic caster, Ainz Ooal Gown.
Under the guise of Count Femel, a noble who was losing favor with the emperor, Jircniv hired the worker groups: Foresight, Dragon Hunt, Heavy Masher, and Tenmu to loot a previously unknown tomb. They also hired the Adamantite adventurer team Darkness and Screaming Whip, to protect the luggage of the workers. Before they set off to their destination, Momon inquired the reasons for the workers for embarking on such a risky job. All of them unanimously stated it to be for money. Others have heard of Momon and Nabe's exploits were skeptical of his reputation. After a brief duel with Parpatra Ogrion, the leader of Dragon Hunt, they were amazed by his skills and abilities against a seasoned former orichalcum adventurer. They had no doubt in their minds of Momon's feat and were convinced of his abilities.
Upon arriving at the tomb, the four teams spit up to search the surface buildings, where they found vast amounts of treasure. They subsequently met up at the entrance of the tomb, upon which Parpatra Ogrion suggested that his team stay behind a look for a second entrance in exchange for 10% of all loot the other workers found and dibs on any major treasure on the lower levels; all parties agreed to this proposition and the other three members entered the tomb. During this time, Momon left the nearby camp in order to oversee and participate in the defense of Nazarick, he had Pandora's Actor take his place.
The workers were immediately greeted by a group of low-level undead, which Gringham dispatched with one blow. This greatly boosted the confidence of the workers who subsequently split up to plunder the tomb, much to the chagrin of Ainz.
On the surface, the other members of Dragon Hunt were discontent with Parpatra's decision. He defended his actions by pointing out that they would be adequately compensated, and even if that weren't the case, it was dangerous to be on the front lines of an unknown tomb. To his surprise, however, they were greeted by the Pleiades led by Yuri Alpha, who complimented Parpatra's prudence. She proceeded to summon the Nazarick Old Guarder to engage Dragon Hunt stating their intention to abstain from fighting. Believing the Pleiades to be the most powerful monsters of the tomb, Parpatra commented that his plan had backfired, the Pleiades only grinned in response. Being no match for the tomb's defenses, the Old Guarders quickly overwhelmed Dragon Hunt. The Pleiades then healed those who were still breathing and sent them to the torture chamber.
Heavy Masher engaged with and quickly fled a number of magic-wielding undead, Elder Liches, who were using fire spells to pursue the intruders. After running for a time, they found a side room and took refuge in it, only to immediately realize that it was a magical trap that teleported them to different parts. Gringham and his thief comrade found themselves in the domain of Kyouhukou. Upon meeting the Druid, they attempted to negotiate but their offers were ignored and were eaten alive by Kyouhukou's children. Another member of Heavy Masher found himself at the mercy of Neuronist Painkill in her torture chambers.
Tenmu had minimal obstacles, a path clear of traps or monsters. Erya Uzruth and his slaves ran into Hamsuke, who was accompanied by a Death Knight and several lizardmen. Hamsuke claimed that the intruders were to be a test for her training to become a warrior; she commented, however, that the worker team was unlikely to be a challenge. Erya Uzruth alone fought the beast, only calling upon his elves to magically buff him with enhancement spells. The two are evenly matched, however, in the end, the human lost after Hamsuke used a newly learned martial art to disarm him. Erya ordered his elve to heal him, but the stood by allowing him to be decapitated by the hamster. After Hamsuke defeated their master, she turned to face the elves only to find them kicking Erya's corpse before collapsing on the ground. Seeing that they had no fighting spirit Hamsuke decided to wait for Ainz's decision on their fate.
After stepping on a magic trap, Foresight found themselves in a large fighting ring similar to one in the Empire. Seeing, the night sky, they thought they had been teleported outside and commented that they could be using flying magic to get away, not realizing that they were on the 6th of Nazarick. But before they could do anything else, they were interrupted by Aura who acted as an announcer and introduced Ainz Ooal Gown, accompanied by Albedo, as their opponent.
Realizing how dangerous their situation was, Hekkeran Termite decided that trying to talk their way out. He started by apologizing to Ainz and requesting to leave unharmed, to which Ainz compared them to being worse than maggots in one's food, and pointing out that you don't simply let maggots go, rather you kill them. Desperate, Hekkeran asked if they could go if Foresight was invited by one of Ainz's friends, Ainz responded by saying he would let them go if such a story proved to be true and asked the leader of Foresight to describe this supposed friend of Ainz. Termite then proceeded to describe his appearance which was quite vague, the nail in the coffin was when he claimed this friend said to "Say hi to Ainz." At which point, Ainz realized this to be a lie since any of his friends would know him as Momonga, not Ainz.
Ainz then went into a fit of rage, cursing them for lying to his face, But he was quickly quelled by the emotion dampener and assured Hekkeran that he understood their situation and couldn't hold such antics against them. He then engaged with the team of workers with a sword and shield, of course, none of their attacks had any effect on him. After a bit of skirmishing, Ainz stated that while he enjoyed a good sword fight, he found himself at a disadvantage against such a well-coordinated team, so he got rid of his weapons and challenged them to come and attack.
This frightened the team as they believed him to be a most difficult opponent as a warrior, and couldn't imagine how powerful he was as a caster. However, after using her Talent, Arche Eeb Rile Furt claimed that Ainz must be bluffing as she couldn't detect any magic. In response, Ainz then took off one of his rings and asked her to try again, upon which the sight of his magical aura nauseated her and threw her into a panic. Her state forced Roberdyck Goltron to use [Lion's Heart] to calm down. Regaining her senses, Arche implored her fellow workers to flee immediately, claiming that Ainz's magic power was at an impossible level. However, Hekkeran checked, and there was no path for escape, so they engaged.
Ainz starts first casting [Touch of Undeath], a spell Arche has never seen. Black fog wraps around Ainz's right hand. Hekkeran sees that Ainz is unguarded and defenseless, but is hesitant to attack due to the risk of the strange magic. Imina shoots her arrows at Ainz, but they are knocked away by Ainz who then teleports behind the half-elf. Hekkeran seeing her in danger charges at Ainz before he could touch her. Activating multiple Martial Arts techniques he strikes Ainz with his twin swords. Sadly the attack is fruitless against Ainz's slashing immunity, leaving the undead unscathed. The Overlord then proceeds to grab him by the head, lifting him off the ground. The adventurer vainly tries to free himself as Ainz tells him that their weak attacks won't be able to touch him. Hekkeran doesn't believe him and cajoles his friends to continue their attacks and look for a weakness. Imina launches her arrows at Ainz, which causes the undead to turn his attention on her. He paralyzes Hekkeran tossing him on the ground.
Roberdyck seeing the hopelessness of the situation orders Arche to use magic to fly away promising to buy her time to escape. Ainz interested in this decides to 'aid' Arche in this endeavor evening opening the gate. Arche hesitant to escape without her comrades complies as the two reminded her that her sisters were waiting for her. Ainz is amused by the development as he expected them to show their disgusting selves but instead saw their deep bond as comrades. However, his admiration does not soothe his anger towards the workers who he perceives to be thieves that dare trespass unto the place he and his comrades built. He orders Shalltear Bloodfallen to chase after the girl and teach her the meaning of terror and to kill her with the deepest and sincerest mercy. The workers are stunned at the sentence Ainz condemns Arche and together they attack him. Roberdyck reaches Ainz first and bears down his morningstar, but Ainz is unharmed so he follows up with a healing spell hoping it would do some damage. Unfortunately, the spell is useless as it hits Ainz's invisible barrier. Imina's arrows likewise are fruitless. The Overlord then appears behind the half-elf, Ainz had used [Time Stop], followed by [Touch of Undead] to incapacitate her.
Once Ainz explains what he had done, the cleric sees that Ainz is a being with unfathomable power. He skeptic about his ability to control time as that is the domain of a god. However, his notions continue to be defined by what he sees. The cleric asks what is to become of them. Ainz speaks of his interest in the faiths of the New World and their origins. He is most curious of how the clerics are able to access Tier Magic, and if their gods are indeed manifest. Sadly the Overlord is unsatisfied with the doctrine of the cleric and his belief in his god, as it is a lack of actual proof. To solve this question, Ainz decides to use Roberdyck in an experiment to help him confirm the existence of the gods. Ainz then orders Aura to bring the bodies of Hekkeran and Imina to Gashokukochuuou.
Meanwhile, Arche flees through the densely wooded area. Briefly taking a breath in the trees, she finds herself being pursued by Shalltear. The young girl then hits a wall in the sky, preventing her from going any further. Shalltear following behind explains that she is actually underground within Nazarick and thus escape was impossible from the beginning. Seeing no alternative and having exhausted all her mana, Arche charges forward at Shalltear who easily subdues her. While in Shalltear's embrace, the former briefly turns into her True Vampire form, the frightening visage causes Arche to summarily faint. Disappointed that she fainted, Shalltear proceeds to kill her. Her body's fate would then be left in the hands of Nazarick's bodies who cannibalized it for various organs and limbs.
The data gleaned during the invasion indicated that the total amount of funds for the defense of Nazarick was minuscule, as not many traps were activated or necessary to eliminate the intruders. The exercise was deemed a success, despite the intruders being too weak. It was predicted that once morning came and the workers failed to return, the adventurers waiting for them would retreat to a safer distance. Albedo then asked Ainz permission to form a unique secret unit that would search for the Supreme Beings. Remembering how Foresight attempted to fool them with the existences of Ainz's comrades' Albedo reasoned that this new group, handpick by her would investigate such claims so Ainz would be informed of the possibility of the Supreme Beings' return. Seeing it to be a sound plan, Ainz permitted the creation of the unit.
While many of the workers were slaughtered, detained, or tortured, only three members of the invasion force were actually spared. The elven slaves of Tenmu; being that they were forced to come against their will into the tomb and thus had no desire for any of the treasures, the elves were spared and given to the Floor Guardians of the 6th Floor: Mare and Aura. The two were sent later to Arwintar to begin the next step of the plan, which was to demand an apology from the Emperor for an official apology. Their arrival would coincide with Emperor Jircniv being informed of the destruction of the hired workers thus beginning Nazarick's formal relationship with the Empire.