He was the creator of Necromancy and one of the most powerful magic users of all time, capable of wiping out entire armies. Once a mortal, Nagash became a lich, casting aside his flesh and humanity in favor of unmatched mastery over the arcane and eternal existence. His goal is to become a god and turn the world into a graveyard under his control. He has been one of the greatest threats the world ever faced, and was only stopped at great cost each time he rose, never being truly defeated.
Rise to Power
Nagash was born in the ancient civilisation of Nehekhara as the son king Khetep, ruler of Khemri. At a young age, he joined the Mortuary Cult and rapidly rose in the rank eventually becoming the High Priest of Khemri. Despite this, he wanted more power and immortality. His chance came when a group of dark elves washed up on the shore of Nehekhara and where brought to him. Nagsh learned from the sorceress of the group the existence of the winds of magic and how to channel them for his own gain. When the sorceress outlived her usefulness, he killed her in a magic duel and consumed her soul. He then proceed with his plan to take over Khemri by bringing together a group of nobles and gave them the ability to prolong their life and in return they swore to serve him forever.
One day he killed his brother, who had succeeded their father on the throne, and buried his wife alive. After tacking Power over Khemri, he started a war against the other kings of Nehekhara. Despite his magical powers, Nagash was defeated and disappeared for a time. During his exil, he founded the forteress of Nagashizzar in the dessert and forged many powerful artefacts, slowly gathering his power to take revenge on his homeland.
Many centuries later in Nehekhara, study of the Books of Nagash by Queen Neferata brought about the creation of the Vampires in the city of Lahmia. When this was discovered by the current King Alcadizaar, he brought his forces against Lahmia to remove the taint of undeath. Despite the efforts of the vampires, the threat of Lahmia was crushed by Alcadizaar's huge army; the Queen fled to Nagashizzar with the six remaining Vampires. Recognising the spawn of his own creation, Nagash made the vampires his captains and sent them back in command of a vast undead horde to conquer Nehekhara. However, he had underestimated his former countrymen. The combined forces of Nehekhara crushed Nagash forces and forced the vampires to flee before his wrath. Enraged by this defeat, Nagash got his allies, the Skaven, to corrupt the River Vitae; it turned black, spreading pestilence throughout the populace. Alcadizaar was forced to watch first as those he loved, including his wife and children died, and then to see his beloved kingdom crumble before him. When Nagash's undead invaded, their ranks swollen by the deaths in Nehekhara, they were led by W'soran and Arkhan, who Nagash had resurrected as a Liche. The meek defenses put up to stop the invasion were easily thwarted and Alcadizaar himself was captured and thrown into a cell to await torture and death at Nagash's pleasure.
He later tries to use a spel so powerful that it would raise all the dead in the world but is stop by the machinations of the skavens who free Alcadizzar and give him a powerful cursed blade known as the fellblade. Alcadizzar use this blade to cut Nagash to pieces and then go out in the desert, consumed by madness. But Nagash didn`t truly die and he would return to plague the world of Warhammer again during the reign of Sigmar, only to be defeated once more.
The End Times
In the End Times, he comes back again, seeking to absorb the wind of death and ultimately the Chaos Gods themselves to become a god. Though initially successful, having consume some of the other races` gods of the afterlife, his plan suffer a massive setback in his battle in Sylvania against a force of chaos daemons when skavens blow up his black pyramid, which was used to amassed magical power. This forces the Great Necromancer to ally himself with the forces of Order to prevent the world’s destruction. In the final battle at Middenheim however, the champions of the Old world fail and the world is destroyed by Chaos with Nagash last being seen strip from his magic and his body crumbling to dust.
Age of Sigmar
He returns somehow in the Age of Sigmar, having consume all the death gods and becoming the sole god of the afterlife. Initialy joining the pantheon of Sigmar and working with the other gods against the invasion of Chaos, he later betrays them and retreat to Shyish, the realm of death. This treachery allows the forces of chaos to crush all resistance and invade all but the realm of heavens. Even Nagash’s domains are all but conquered and The Great Necromancer himself his struck down by Archaon. Returning back to life after his defeat, he is curantly ammasing his power in a sub-realm to retake what is rightfully his.