Pleiades

Pleiades (プレアデス) is the combat maid squad of the Great Tomb of Nazarick. Its members originally only served as Nazarick's last line of defense, but Ainz Ooal Gown has assigned them more tasks after the tomb was transported.

Background
The Pleiades is the combat maid squad of Nazarick, programmed as sisters. They fight under Sebas's command as a final raid boss team right before the throne hall. All of them are women of unsurpassed beauty, each with a different type of appeal. After the teleportation to the New World, three of them are working outside of the tomb. This seems to be because they are amongst the rare NPCs from Nazarick who can easily disguise themselves as humans.

The Pleiades can be organized in two different formations. One is the "Pleiades Six Stars" and the other is the "Pleiades Seven Sisters". These formations can be switched by changing the leader to Sebas Tian or Aureole Omega. The "Pleiades Seven Sisters" activates in Volume 6, yet Ainz does not allow her to move and thus, Yuri Alpha becomes deputy leader.

The Undead King Arc
Momonga orders the Pleiades to guard the 9th Floor for possible intruders in the Great Tomb of Nazarick. They also guard and escort Momonga around Nazarick before making an excuse and won’t allow anyone to follow him.

The Dark Warrior Arc
Ainz Ooal Gown choose Narberal Gamma to be his adventurer partner and infiltrate the fortress city of E-Rantel. Their plan is to become famous adventurer so that they can gain more information about this world.

The Bloody Valkyrie Arc
In E-Rantel, Shalltear Bloodfallen's task was to enslave any criminals who knew martial arts or magic talent. While Sebas Tian and Solution Epsilon have been ordered by Ainz to disguise themselves as humans, and gather information. In particular, the roles they played were an elderly butler and a spoiled rich princess. As well in E-Rantel, Narberal stay at the inn and wait for Ainz's instruction when he returned.

The Show Must Go On! Arc
Aura informed Albedo that the Pleiades opted to refrain from entering the Romeo and Juliet auditions, for the role of Juliet.

The Two Leaders Arc
One of the Pleiades, Lupusregina Beta, was stationed at Carne Village to protect Nazarick's assets: Lizzie Bareare and Nfirea Bareare.

The Maid Tea Party Arc
The Pleiades, with the exception of Lupusregina and one other, assembled at the Great Tomb of Nazarick to hold their monthly report and tea party.

The Men in the Kingdom Arc
After being questioned by authorities, Sebas leaves while Solution finally decides to contacts Ainz and informing him that Sebas might have gone rogue. After confirming Sebas' loyalty, Ainz then switches the Pleiades Six Star to the Pleiades Seven Sister. Since Aureole Omega won't be move from her post, Yuri Alpha will be the temporary leader instead.

The Pleiades participated in Demiurge's plan to make Momon, a hero in the Re-Estize Kingdom. The Pleiades acted as Jaldabaoth's underlings with their faces disguised with masks with the exception of Narberal Gamma, who as Nabe, assisted Momon during the disturbance. Operation Gehenna commences, Nabe will fought against Lupusregina, Solution and Entoma, while Evileye will fought against Yuri and CZ until Jaldabaoth ordered a retreat.

The Invaders of the Large Tomb Arc
Before the slaughter of the workers, Ainz returns to the tomb, leaving Narberal and Pandora's Actor at the adventurer's encampment. Pleiades meet Green Leaf on the surface of the Tomb. Yuri Alpha orders the Nazarick Old Guarders to fight against Green Leaf. However, Nazarick Old Guarders easily defeat Green Leaf without having to deploy any of the other servants.

The Magic Caster of Destroy Arc
When the delegation from the Baharuth Empire arrived at the doorstep of Nazarick, the battle maids entertained them, serving them delicious drinks. The members of the delegation were impressed by their discipline and attractive looks.

The Pleiades Day Arc
Upon completing all her assignments for the day, Yuri Alpha returned to her quarters where she found Narberal Gamma and Lupusregina Beta relaxing. Yuri tensed with frustration scolded them for their uncouth behaviors was called by Ainz Ooal Gown to assist him in a dispute with her sister Solution Epsilon, who had stolen his bathing attendant Miyoshi. Yuri manages to compel the slime to give up her captive and return him to Ainz. Rather than punish her Ainz, sees it as a sign of his neglect, and decides to have Yuri investigate the desires of the other Pleiades.

Ainz’s Ambition Arc
The Pleiades were summoned by Albedo to attend Ainz's during his three day vacation along with the entire Nazarick work staff.

The Paladin of the Holy Kingdom Arc
and The Paladin of the Holy Kingdom II Arc The Pleiades, specifically Yuri, Lupusregina, Solution, Shizu and Entoma, under the alias as Jaldabaoth's Demon Maids were used as a bargaining chip in the negotiations with the Holy Kingdom Liberation Army and the Sorcerer Kingdom. Though the resistance had yet to confirm these maids in the Northern Holy Kingdom, they agreed to allow Ainz to take control of them once he had dealt with Jaldabaoth.

During the Sorcerer King's fight with Jaldabaoth and his associates, Erich String Orchestra, a group of Greater Doppelgängers take on the form of every member of Pleiades except Aureole Omega and Narberal Gamma. These doppelgängers borrowed the Pleiades equipment and received a buff from Aureole Omega prior to encountering and fighting Ainz in a match.

In the end, Jaldabaoth defeated the Sorcerer King while heavily covered in wounds. Despite losing to him, Ainz was able to successfully freed one of their demon maids, CZ2128 Delta from Jaldabaoth's control.

Strength
With all of them except Sebas and Aureole Omega being under level 65, the Pleiades's combat capability is quite low considering the role they have been given. This is because the final defense line of Nazarick is actually concentrated on the 8th Floor. The actual purpose of the Pleiades is just to delay the invaders, allowing all the guild members enough time to gather together in the throne hall and greet the invaders like villains in fiction.

Despite being look upon as weak by YGGDRASIL standard, the levels of each member in this group from the New World's perspective makes them an equivalent to legendary monsters.

While the Pleiades each had completely different job abilities, their maid skills were all equally the same. For instance, they can still perform housework like the Homunculus Maids under the command of Pestonya. In a sense, they could substitute for each other in a professional capacity.

Known Members

 * Sebas Tian - Leader of Pleiades Six Stars
 * Yuri Alpha- Deputy Leader
 * Lupusregina Beta
 * Narberal Gamma
 * CZ2128 Delta
 * Solution Epsilon
 * Entoma Vasilissa Zeta
 * Aureole Omega - Leader of Pleiades Seven Sisters

Trivia

 * The dual organization of the Pleiades refers to two different meanings of the word "Pleiades". In Greek mythology, the Pleiades refer to the seven sisters, daughters of the titan Atlas, while in astronomy the Pleiades is a star cluster called the "Six Combined Star" (六連星) in Asia.
 * The homunculus maids of Nazarick think of the Pleiades as a kind of idol group, with CZ the most popular among them.
 * The members of the Pleiades called each other sisters, but unfortunately they were not true sisters, since they were made by separate creators. They were simply designed to be that way.