Undead

The Undead are a group of sub-races that share a universal trait; they have already died once, but their soul remains, either by itself or in its former body, and they cannot die from old age, allowing them to technically live forever as long as they are left alone.

Undead have a variety of abilities, depending on their race and type.

The creation of an Undead can come from two things, from a curse or spell, or, if they weren't able to pass on peacefully and/or refuse to ascend, they will become a ghost.

A big downside for most Undead is that many people fear them. Zombies, especially, might not be allowed in some places due to the fact that they're stinky, rotting corpses, although skeletons are typically more respected.

Zombies
Zombies are the most uncommon form of the Undead, as they are typically the first stage and the one that can last the shortest.

Zombies are, simply put, spirits that refused to leave their body, although it's already dead. This causes them to take a pale, blue appearance (unless their body was embalmed) and eventually their flesh will begin to rot and decompose.

As their bodies are already dead, they are capable of pushing their bodies to new limits. They don't have to worry about sleep, exhaustion, or even pain. And, since over time their flesh and muscle will become weaker and softer, they will be able to become much more flexible as well. They also gain a decent boost in their strength.

Their main weaknesses come from being weaker to holy magic and soul-enchanted weaponry, which can both directly hit the spirit inside their body. Their flesh also becomes weaker, and can fall and be ripped off much more easily the more it decomposes.

Skeletons
Skeletons are one of the two more common types of undead. They are basically the skeleton of someone, held together and strengthened by the soul inhabiting it, which is almost always the soul that the skeleton belonged to.

Skeletons are created most commonly when a Zombie's flesh decays completely, leaving only the skeleton left. Although, a ghost or other spirit can possess a skeleton itself, although this is much more uncommon.

They share most of the strengths and weaknesses as a zombie, such as strength, no pain, and holy and soul magic/weapons hurting them more.

Ghosts
Ghosts are typically the most common, yet hardest to see form of undead. They are simply the souls of the dead who haven't passed on, be it by choice, not feeling comfortable about it, or even a curse. If a Skeleton or Zombie's body is destroyed by any means other than a soul-enchanted weapon, they will become a ghost.

Ghosts have a variety of abilities, much more than the others. They can levitate, phase through objects, hide inside objects (called Haunting), hide and show themselves from view of the living, and if strong enough, even be able to possess living beings.

Ghosts are incapable of being harmed by traditional weaponry, so the only way to attack them is with soul-enchanted weaponry.