8th Floor Hierarchy

8th Floor Hierarchy is the generic term referring to a group of powerful NPCs which resides on the 8th Floor within the Great Tomb of Nazarick.

Background
The 8th Floor is guarded by Victim and the far more powerful NPCs working under it. They were the last line of defense who had the task of stopping invaders from getting pass the 8th Floor. They are still regarded as such to be Nazarick's final defense force even after being transported into the New World. In the past, they successfully put an end to the largest invasion to have ever occurred throughout the history of YGGDRASIL.

Their floor was considered the only location around in Nazarick which the other Floor Guardians except Victim know hardly a thing about especially those residents who are part of the 8th Floor Hierarchy. In the Web Novel, Floor Guardians assumes that the existence of an 8th Floor Hierarchy was also made to destroy them in the event that they rebelled against Ainz.Overlord First Half Chapter 79: Gaiden Guardian Aura-chan

The Undead King Arc
After being transported into the New World, Momonga gave an order to the Pleiades that they will head to the 9th Floor and repel any possible invaders coming from the 8th Floor if found.Overlord Volume 01 Chapter 1: The End and the Beginning

Meanwhile, Ainz recalls the time when the invasion of 1500 people (players and NPCs) from the Union of Eight Guilds having managed to find their way down to the 8th floor.

When Albedo informs Ainz that she will investigate the 8th Floor and its inhabitants, the latter warns her to be careful while over there. He reminds her that if an emergency situation occurred from the 8th Floor wherein which the problem cannot be taken of, she must contact him immediately about it. However, Ainz later changed his mind and orders Albedo along with the other Floor Guardians not to enter that floor from now on.Overlord Volume 01 Chapter 2: Floor Guardians

The Bloody Valkyrie Arc
According to Sebas Tian, he hinted that there was most likely a powerful force residing in the 8th Floor of Nazarick as the invaders were never able to successfully get pass that floor alive. Besides knowing the fact that Victim is part of the 8th Floor, Shalltear Bloodfallen began to wonder what other mysterious beings are living in that place. She starts speculating that maybe the likelihood for one or possibly more of the these unnamed entities are somehow Ainz's personal creation.

However, Sebas puts her idea to rest as he states that there was a rumor in Nazarick about Pandora's Actor being the NPC created by Ainz rather than those from the 8th Floor. Sebas made his own speculation that there might be some sort of mechanism put in place for the 8th Floor to not only fend off intruders, but fellow denizens from other floors in Nazarick as well. In the end, the two kept the idea of visiting the 8th Floor on hold until Ainz decides to give them permission to go there.Overlord Volume 03 Chapter 1: Herd of Predators

The Lizard Man Heroes Arc
It was said that the guild weapon of Ainz Ooal Gown can be found on the 8th Floor. Ainz noted that among those of the 8th Floor Hierarchy, Aureole Omega was the person he have chosen to be given the duty in safeguarding it from any harms way possible.

Ainz recalls an experiment he had committed at some point in time, using "The Creation" super-tier spell to cover the entirety of the 8th Floor.Overlord Volume 04 Chapter 5: The Freezing God

The Two Leaders Arc
Some of the Homunculus Maids felt that the outside world was inferior to Nazarick, but most of them were afraid of it, because the 8th Floor and the Hierarchy right above their home, had once been invaded by people from the outside.Overlord Volume 08 Side Story 2: A day of Nazarick

The Invaders of the Large Tomb Arc
When Albedo made a request to Ainz that she wants Rubedo in her unit, Ainz rejects that person from joining the group at first, but caved in shortly after hearing the Overseer's reason for having her young sister take part.

On the other hand, the chance in winning against Rubedo is extremely low for Ainz who believes it as so. Ainz admits that the NPC would most likely defeat him even if he was fully armed and equipped with his main gear. Therefore, Ainz remarks on the only possible way to defeat Rubedo is if he depends on those from the 8th Hierarchy who have the potential in being able to defeat it. At the same time, he was willing to equip the 8th Hierarchy with the guild's World Items in order to ensure their victory is a guarantee.Overlord Volume 07 Chapter 4: A Handful of Hope

The Paladin of the Holy Kingdom Arc
During Ainz's fight with Jaldabaoth and his demon maids, he deduced the source of the group's power came from one of the 8th Floor Hierarchy, Aureole Omega. Knowing that she could have not left the 8th Floor without his permission, Ainz wonders whether she has buffed them ahead of time, but then considered the idea that maybe it was the work of a Doppel-Aureole Omega instead. In the end, he decided to push these thoughts aside in order to focus on the battle at hand.Overlord Volume 13 Chapter 5: Ainz Dies

Strength
The 8th Floor Hierarchy are considered to be the most powerful force of unknown NPCs throughout the Great Tomb of Nazarick. On the 8th Floor, they have the strength to withstand and annihilate 1000 to 1200 players among the 1500 invaders hailing from the Union of Eight Guilds.Overlord First Half Chapter 79: Gaiden Guardian Aura-chan They are also viewed as being Nazarick's maximum strength. Those of the 8th Floor Hierarchy are extraordinarily strong and a large amount of them had their MP almost depleted after the battle was over.ARCADIA 2.47: ARCADIA 2377 4-10-2011

From the words of Momonga, the 8th Floor was said to secretly contained "Nazarick's largest trump card," suggesting that they may have play some important role in actually defeating them. After failing to conquer the 8th Floor Hierarchy, the defeatists labeled their "trump card" a cheat and never once again bother to combat Nazarick afterward.Overlord First Half Chapter 48: War Part 8

There are also a few individuals in the 8th Floor Hierarchy who had the actual power to combat Nazarick's strongest NPC, Rubedo, and only if they were to use World Items on her.

The author Maruyama states that Ainz's chances of obtaining victory over the 8th Floor Hierarchy are estimated to be 30% even if he was to use all the equipment borrowed from his fellow guild members.ARCADIA 2.9: ARCADIA 226 05-26-2010 Regardless, entities of the 8th Floor Hierarchy are stronger than Ainz according to Maruyama.ARCADIA 2.24: ARCADIA 746 10-18-2010

However, the 8th Floor Hierarchy isn't as invincible as it may seem for some players out there especially the top-tier ranking ones. Maruyama notes that if the top 100 players join in together during the assault on the 8th Floor, it was very possible for the Hierarchy to be defeated by them. While not all of them are completely annihilated from the battle on the 8th Floor, they can still overcome the rest of Nazarick and make it fall 100% thereafter.ARCADIA 2.32: ARCADIA 910 10-31-2010

NPCs

 * Aureole Omega (Light Novel Only)
 * Rubedo (Light Novel Only)
 * Victim (Light Novel Only)

Trivia

 * Half of Ainz Ooal Gown's funding was invested in the 8th Floor of Nazarick.ARCADIA 2.36: ARCADIA 1088 10-28-2010
 * On the 8th Floor, there exists a Cherry Blossom Zone that resides one of the 8th Floor Hierarchy, Aureole Omega.
 * Entry to the 8th Floor is forbidden under Ainz's order. In short, it is the particular floor in Nazarick which will only be effected with his authority.
 * Momonga noted that the reason why there were no POP monsters on the 9th Floor in the first place was simply because if any intruders could overcome the 8th Floor Hierarchy, the most powerful beings in the Tomb, then Ainz Ooal Gown’s chances of victory would be slim. The author Maruyama even mentioned the fall of Ainz Ooal Gown is inevitable if that did happen.Kugane Maruyama's Tweet: July 31, 2015
 * Blazing Temple was said to be the area that is near the Gate which allow intruders to enter the 8th Floor where the Hierarchy is located in.Overlord Volume 01 Chapter 3: Battle of Carne Village
 * In the Web Novel, Ainz thought that if YGGDRASIL players have no intentions of becoming his allies, he considers using every means necessary including the 8th Floor Hierarchy to eradicate them.Overlord First Half Chapter 50: War Part 10
 * According to Maruyama, not everyone from the 8th Floor Hierarchy will likely make an appearance or have screen-time in the Overlord series.ARCADIA 2.31: ARCADIA 879 10-05-2010ARCADIA 2.42: ARCADIA 1502 2-06-2011