Necromancy

An art that's forbidden in most cultures. Necromancy is the revival of the dead, an advanced form of spirit calling where through a variety of dark, mysterious rituals, necromancers are able to summon the souls of the dead and then bind them into a vessel, most commonly into a deceased body. The revived are dubbed 'Undead', deceased souls that have been brought back once again in an undying state, unable to refuse the will of their Necromancer.

Human necromancers, even if they're a master in the art, can typically summon no more than three hundred undead, with the average being at around ten for an experienced Magi. This number becomes lower depending on the power of the souls they've brought back, for instance, if a powerful Magi is brought back, this may count as a hundred standard  undead.

History
The founder of this magic is Azrael. His desire was to use it as a means of ending death and war--humanity would be put in a state of undeath, bound to his will. Azrael's abilities in necromancy were the most advanced example known to date... The undead possessed self-regenerating bodies and true immortality, and at the peak of the second divine war he had hundreds of thousands of undead under his command.

Azrael's initial creation of necromancy comprised of rending apart the barrier between the earth and the heavens- Permanently scarring and rending the barrier that would ordinarily protect the stars from mortal meddling. The very act lead to his fall, staining his wings black with the selfish shortsightedness and utter madness it required.

Whilst many necromancers have practiced their art throughout all the nations in history, the most notable one of recent history is Lord Kyros, the immortal Lich Oscuri lord of Valmasia, one of the three lords of the ever expanding Valmasian Empire who conquered Valmasia under Azraelite rule since the 10th century.

Binding the Undead
What's commonly known is that a necromancer usually requires a fresh corpse to ensure a successful revival. Necromancy is a complex art and without a tome or a teaching it's almost impossible to replicate. This usually involves in detail:
 * Ritual preparation. The necromantic runes used on the deceased as a beacon into the afterlife, using their body as a link of sorts.
 * Calling the soul back to the living realm, by establishing a connection between it and its deceased body. During the ritual, the necromancer's essence will head into the stars, an otherworldly plane where they can easily get lost, and physically die, if they're not focused on their objective.
 * The soul will likely resist the call, and force must be used. Once the soul is in the physical realm, the necromancer will call it down and attempt to ease it into the target; often coaxing it by having belongings nearby, or friends and family. Alternatively, they may be more forceful and use their brute power to pull the soul down. The stronger the person was in life the more difficult their soul tends to be if the call is rejected.
 * If the soul does not reject its host, the subject will awaken as an undead.

Playing an Undead
Most countries consider undeath to be an aberration on the natural order, with stories of undead being slave-bound tools of the necromancer and twisted, sociopathic forms of their former selves commonly shared between campfires. Valmasian undead are the most advanced, lifelike form of necromancy currently known, where the ability is considered a cornerstone of their empire. Tens of thousands of undead make up the armies that have been slowly conquering the terrorities of Brittania since the 1300s. For the most part, these soldiers are simple skeletons, but the magi that're given special treatment do not rot to the bone, maintaining some physical semblance of their past self as well as most of their magical potency.
 * No sense of taste, unable to digest food, produce bodily fluids, or feel stimulating pleasure (from the senses, or sex).
 * Drastic personality changes are common, caused by the process of being revived. Jumbled memories, bouts of rage and anger, edging deeper on to the chaos spectrum emotionally.
 * Rotting flesh, with a faint aura of decay that is more prevalent the more corrupt the magi becomes. This occurs because the soul requires a living, aging body or it's not compatible.
 * Subservient to their necromancer's commands, though they may try to break control.

It's still a far cry from Azrael's undead, mind, who could revive the fallen to youthful versions that could regenerate flesh, impervious from injury.