Shaman Elder Ner'zhul was the Warchief of Draenor, one of the clans left uncaptured after the destruction of the Dark Portal on Azeroth. He was tricked into making a blood pact with Kil'jaeden the Forger; the one who introduced the Orcs into the Burning Legion. After the Second War, he opened many portals on Draenor in an attempt to find new lands to escape and conquer, but was immediately captured by Kil'jaeden. His mortal form was destroyed and his spirit was transformed into the spectral Lich King, who was encased in the mystical ice of the Frozen Throne on the Icecrown glacier in distant Northrend.
Rise of the Horde: Ner'zhul was the chief and eldest shaman of the Shadowmoon clan and one of the most popular figures in Orc society. He was admired, respected and revered by all given his deep connection with the spirits, and he was the closest thing to a leader the Orcs had before the creation of the Horde. But, deep within his being, Ner'zhul yearned for a power that he did not have ... One day, Ner'zhul contacted the spirit of his companion, Rulkan, who alerted him to the threat of the Draeneis, who (according to him he said) conspired to destroy the Orcs. Many moons later, she introduced him to Kil'jaeden, "The One", who began to instruct him in the ways of witchcraft and betrayal of the Draeneis. Although Ner'zhul was elated at the prospect of saving his people (and finally being recognized as he deserved), he was puzzled that the ancestors no longer spoke to him and were very distant.
Ner'zhul managed to unite the rest of the clans to begin attacking the Draeneis settlements, supposedly by order of the ancestors, but the more he saw the Draeneis the more confused he was; Apart from horns, clothes and skin tone, Kil'jaeden bore a great similarity to the Draeneis and he possessed Many (Leader of the Draeneis for more than 25000 years, a great friend in his day of Kil'jaeden himself) unfit for a "divine" being like him. Searching for answers, he attempted to commune with the ancestors in Oshu'gun, the "Mountain of Spirits". He was horrified when the ancestors greeted him like a monster, and the "real" Rulkan revealed the truth: Kil'jaeden had been lying to him all this time.
Ner'zhul decided to challenge your demon master, but Gul'dan, his apprentice, who followed him up to this point and, grateful for his current new power, informed Kil'jaeden of the shaman's betrayal. Kil'jaeden, rewarded him for his great service, elevating Gul'dan to the position of Ner'zhul, and he was relegated to a merely decorative position, stripped of his powers. Kil'jaeden forced Ner'zhul to help the orcs fall into bloodlust and witchcraft. He could not prevent the rise of the Shadow Council, knowing all its secrets but unable to reveal them.
But Gul'dan was very careless. Thinking that Ner'zhul lacked all power, he allowed his former master to access all the documents held by the Shadow Council, and this is how he discovered that Kil'jaeden planned to feed the Orcs with the Mannoroth Blood (Pact that would bind the Horde to the Legion for their entire existence). But, with the little reputation that he already maintained, no boss listened to him, save one.
As a result of Ner'zhul's warning, Durotan, chieftain of the Frostwolf clan (Thrall's father) refused to allow his clan to drink Mannoroth's blood and saved it from the worst of corruptions. Durotan and his partner Drake, they were the only ones who knew about Ner'zhul's actions - a secret that died with them years later. Today, no one knows that one of Azeroth's greatest enemies saved the Orcs from complete annihilation.
Beyond the Dark Portal: Following the defeat of the Horde in the Second War, the Alliance pressured the Horde to retreat to the Blasted Lands, eventually destroying the portal. On Draenor Ner'zhul was hit by the shock wave and badly injured. For two years the clans fought each other until Sanguine Theron (Gul'dan's acolyte and great necromancer, the first death knight created by dark magics to combat powerful Human wizards) devised a plan to open many portals to different worlds in order to conquer them by the Horde. Teron asked Ner'zhul to be the leader of the Horde again. Ner'zhul recovered, he isolated his clan in the Valley shadowmoon, where he had visions of death (mainly about his future destiny). He painted a white skull on his face. When Sanguino became Undead, he appeared before him, Ner'zhul, who was not surprised, and after persuading him agreed to carry out the plan to open many portals. In order to fulfill the plan he searched for various artifacts from Azeroth: the Gul'dan Skull, Book of Medivh, el Sargeras Jeweled Scepter, and the Eye of Dalaran, a device created by the human wizards of Dalaran to focus magic together to rebuild the Violet Citadel after the Second War.
The first object he acquired, the Gul'dan Skull, soon began to influence the old shaman. His rebellious apprentice spoke to him through his remains. Ner'zhul cared more for the future of his own power than that of the Horde.
After obtaining the rest of the items, he attempted to open the portals on Draenor. Sensing the flow of power that came to him after taking over Draenor's magical powers, Ner'zhul ended up not caring for the well-being of the Horde, thinking only of harnessing his new powers. In his arrogance, he ordered his followers to go after the portals, leaving the Horde behind. Obris (chief of the Joking Skull clan, a very high-level member of the Horde), one of their servants, protested Ner'zhul's decision to abandon the rest of the Horde. In response, Ner'zhul attacked him; without hardly weighing it. Flooded with a power he could never dream of, greed overwhelmed him, and all vestige of honor and altruism that remained vanished as he and his followers passed through the portal, abandoning the rest of the Orcish Horde to their own fate. The tremendous energies of magic he created destroyed the world as Ner'zhul fled, giving rise to the devastated kingdom of Outland.
The birth of the Lich King: As soon as they entered the portal, Ner'zhul and his followers were immediately seized by Kil'jaeden. All died except the old shaman, whose spirit was kept safe. Agreeing to serve the demon once more, Ner'zhul was brought to the Frozen Throne. His perception, mental powers, and magical abilities expanded enormously. The Lich King had been born. As the Lich King, Ner'zhul would rule the Scourge only until Arthas Menethil arrived, who would later consume his spirit and become the Lich King.
Let's remember the final scene of Warcraft III: The Frozen Throne, in the Ascension, like Arthas after fighting and Get Frostmourne (Frostmourne), free the soul of Ner'Zhul, they fight an inner struggle in which Arthas "wins", becoming the current Lich King.
Continued ...