Before Naxxramas, before the lich, and before the famous laugh, Kel'Thuzad was a man from Dalaran.
A remarkably successful one at that: an archmage of the Kirin Tor, a member of the Council of Six, and a wealthy, influential mage.
His interest in necromancy ruined that career.
Antonidas forbade such research, but Kel'Thuzad continued. He was eventually stripped of his position and exiled from Dalaran.
Around that time, he heard a voice calling from Northrend.
Key Events
The Road to Icecrown
Ner'zhul was already bound within Icecrown and subjugating the north, but he needed living agents for the coming war against the human kingdoms.
He began calling to mages who might be tempted by forbidden knowledge and power.
Kel'Thuzad answered.
The journey north quickly showed him what he had joined. Along the way, he saw Scourge-held lands, the undead, and the consequences of Ner'zhul's rule. According to his own account, the mage was openly terrified at one point.
He did not turn back.
Kel'Thuzad reached Icecrown and offered Ner'zhul his service.
An Emissary Among the Living
The Lich King did not immediately transform his new servant into one of the undead.
Kel'Thuzad was more useful alive.
He returned to Lordaeron and founded the Cult of the Damned. It recruited from every level of society, from nobles to exhausted laborers and farmers. People were promised eternal life, equality, and a place in a new order.
That sounded rather more appealing than “help us turn the kingdom into a graveyard.”
The cult grew in secret for several years. It forged ties with the Barov family, Scholomance, and Baron Rivendare. Through this network, the Scourge could operate inside Lordaeron before the invasion began in the open.
Ner'zhul finally had agents who could walk through human cities without attracting attention.
The Plague Came After the Cult
Once the network was ready, Kel'Thuzad began spreading the plague of undeath.
In Warcraft III, Arthas and Jaina follow his trail as they investigate the plague in Lordaeron. Arthas catches the necromancer near Andorhal and kills him.
Before dying, Kel'Thuzad directs him onward—to Mal'Ganis and Stratholme.
There is a dark irony in the campaign: the player first kills Kel'Thuzad through the still-living Arthas, then later, as the fallen Arthas, carries his remains to the Sunwell for resurrection.
Kel'Thuzad then returns as a lich.
Why Players Remember It
Stories about the Scourge quickly become stories of zombies, plague, and undead armies. Kel'Thuzad matters for a different reason: the first real bridge between Ner'zhul and human society was built by a living man.
The Lich King could not yet lead armies through Lordaeron in person.
But he had a former mage of Dalaran with wealth, connections, and an understanding of what might tempt people.
The plagued grain, Stratholme, and Arthas's fall came later.
The Cult of the Damned had begun its work first.
And it was founded by a man who made the entire journey to Icecrown of his own free will.