Undead

Undead (アンデッド) are creatures that have come back to the land of the living after dying and are found both in YGGDRASIL and the New World.

Background
In YGGDRASIL, undead was one of the many races a Player can choose to be. Moreover, such race is divided into different subspecies according to their racial level, allowing players to further evolve beyond it. This goes along well with the right classes specifically that are befitting for someone who was an undead. A necromancer for starters was a class that allowed one to gain control over an undead or create one as their own slave.

However, the quality of the undead produced can vary depending on the species of the corpse especially ones in the New World. The best corpses for example were those of powerful beings like dragons. In particular, human corpses are one of the few races that were shown to to have turn into zombies and skeletons. This was shown, when an undead player such as Ainz is able to turn a mere human corpse into the form of a Death Knight. There are even some among the Dragon Lords, one of the strongest species from the New World who're an undead themselves.

For Ainz to create a permanent undead that cannot disappear easily until killed in battle, he needs the target's dead body or any least bit of their remains including bones to carry it out. In some shape or form, his way of using the corpses seem as if a resurrection is taking place, yet the targets that are dead will come back to life as an undead rather than alive in the flesh through a racial skill. Though it is different from a normal resurrection via a tier spell, where the person is supposed to be brought back to life not as an undead, but part of the living instead.

For Ainz, he is able to spawn an undead out of thin air by using one of his racial skills as Overlord, a high-tier race. Yet the undead created were only able to stay in the New World temporarily since it wasn't done with a corpse or any parts of its body, which create a permanent undead. Even mid-tier or higher-tier undead monsters can spawn a weaker undead through the person killed by them. Depending on the undeads' abilities like Crypt Lord or Overlord, they are also able to make their own weak undead minions stronger than normally was supposed to be while controlling them.

On the other hand, the undead are looked upon as monsters that possess an undying hatred for all living creatures and its intent was to eradicate them. It was the reason why the undead are considered to be the enemy of all living beings negatively. Yet, there are few exceptions to this idea in which Ainz Ooal Gown and Davernoc, who doesn't see it the same way they do, but was still indifferent to them nonetheless in terms of not being able to show emotions physically. Despite Yuri Alpha being an undead, she doesn't seem to bear any ill hatred towards the living and regarded some of them with kindness instead. Also, the same could be said with Evileye, an undead who works in a group like Blue Rose consisting of humans.

Although the undead possesses hatred against the living, there are some who're able to somehow suppress it and reach a mutual understanding with them to some extent. In other words, certain sentient undead are capable of keeping their hatred under control when negotiating and forming relations with the living. If the living were the ones who try to offer negotiation first, then it would usually end up turning out to be a bad trade. But if the undead were to initiate the first offer or negotiation, there had once been instances of people obtaining ancient items that had been made with now-forgotten knowledge. Whenever Ainz issues mental commands over the weaker undead, they won't be able to easily attack the living out of their nature unless it was ordered to do so by their master.

While so, the undead do not age, so they would continue ruling the land for all eternity until it was defeated. Unlike the dragons' own growth rate, high-level undead are not the type to grow in bodily might. They could instead accumulate knowledge and experience constantly over time. From that point of view, the undead might be even stronger than dragons. The undead do also happen to have absolute resistance to the effect of mind control spells. Simply put, controlling the minds of undead with magic is next to impossible unless it was done through a World Item such as Downfall of Castle and Country.

When a group of weaker undead gather in one place, stronger undead are then created after a certain period of time passes by. Undead normally spawned in places such as the Katze Plains where many people died. For example, a Death Knight and other undead spawning at that location tends to be a hotspot for their birth. Such effect could also be used in tangent alongside a magic ritual called Death Spiral that turn a living person into an undead like the Elder Lich. Though this ceremony requires the sacrifice of a location composed with living entities to form another place for naturally spawn undead. They gather together in numbers, causing the birth of a more powerful undead to appear one after another while the cycle continuously repeats itself.

In the New World, it seems there are legendary tales recorded and passed down about the undead. One being the Soul Eaters, which devoured the souls of the living. While another case being the Wriggle Pestilences, which spread disease. Additionally, there are mage cabals which gathered many undead around a core of Elder Liches for instance. And then there was Guphandera Argoros, the undead dragon that lurked in a mountain of the dead and is a user of psychic-type magic. Not only that, but this also includes the Astral Rippers, masses of shadows which stalked the Valley of Shadows, and so on.

Although the undead could be dominated through magic, the only human who succeeded in doing so was one of the Thirteen Heroes being Rigrit, a necromancer. However, dominating the undead requires a rather complicated process even for the likes of Fluder to master. Basically, the control and destruction of undead should be done by priests using the power of god. If one chooses to become an undead in the New World, their heart and mind will begin to alter as well. The change to the undead state often affects the soul too as far as Evileye knows it, since she is an example of one who was once a human being.

Basic Undead Race Traits

 * Bludgeoning Vulnerability V
 * Biological Penalties' Resistance
 * Critical Hit Immunity
 * Dark Vision
 * Death Immunity
 * Disease Immunity
 * Doubled Damage by Fire
 * Eating, Drinking, and Breathing are Unnecessary
 * Energy Drain Immunity
 * Good, Light and Holy Vulnerability IV
 * Good and Holy Consecrated Areas' Vulnerability II
 * Mind-affecting Immunity
 * Necromancy Resistance
 * Paralysis Immunity
 * Physical Penalty Resistance
 * Poisoning Immunity
 * Recover by Negative Energy
 * Sleep Immunity

Skeleton

 * Bone Vulture
 * Elder Lich
 * Nazarick Elder Guarder
 * Nazarick Master Guarder
 * Nazarick Old Guarder
 * Overlord
 * Skeletal Dragon
 * Skeleton Archer
 * Skeleton Centipede
 * Skeleton Mage
 * Skeleton Rider
 * Skeleton Warrior
 * Soul Eater

Zombie

 * Blood Meat Hulk
 * Corpse Collector
 * Death Knight
 * Dullahan
 * Eyeball Corpses
 * Freezing Zombie
 * Frost Bone
 * Ghast
 * Ghoul
 * Jack the Ripper
 * Necrosome Giant
 * Organ Egg
 * Plague Bomber
 * Squire Zombie
 * Undead Beast

Death Spirit

 * Astral Reaper
 * Carrion Baby
 * Grim Reaper Thanatos
 * Ghost
 * High Wraith
 * Pale Rider
 * Wight
 * Wraith

Vampire

 * Elder Vampire Bat
 * Lesser Vampire
 * True Vampire
 * Vampire Bride
 * Vampire Princess
 * Vampire Wolf

Unknown Undead

 * Corrupt Dead
 * Crypt Lord
 * Death Cavalier
 * Death Emperor
 * Death Empress
 * Eternal Death
 * Swell Skin
 * Vampiric Dragon Lord
 * Elder Coffin Dragon Lord
 * Guphandera Argoros

Trivia

 * The Baharuth Empire is conducting experiments to make undead laborers under their control. However, it seems apparent that Ainz is already doing just that with his undead minions, lending them out to the citizens and dealers of his nation for various tasks.
 * Those who died a violent death and the dead who were not properly revered have the highest chance of becoming undead.
 * It is uncertain what causes the spontaneous genesis of the undead, the Baharuth Empire is currently investigating the reason.
 * To prevent the dead from becoming undead, the people of the New World have taken to making proper burials for the dead as soon as possible when death occurs.
 * Albedo once tried to conduct an experiment to determine which type of undead could feel emotions, but her findings were cut short after she got into an altercation with Shalltear.
 * There exists a secret society that only consisted of undead Magic Casters.