The Nerubian Empire was the home of the Nerubians until the Lich King defeated them. Parts of it, once an underground network that stretched nearly half the breadth of Northrend, can still be found beneath Northrend.
After the Azj'Aqir, the Empire of the Aqir, was shattered by the Gurubashi and Amani Trolls, the nerubians fled north and founded their empire in the northern wastes. It's unknown what effect the Great Sundering had on it, but they developed to a high culture with great architecture and created an kingdom beneath the frozen wastes of Northrend. The capital was called Azjol-Nerub, sometimes generalized for the whole empire.
War of the Spider
When the Lich King became stronger, he began to battle with the Nerubians in a war called the War of the Spider. After ten years of fighting the Undead managed to enter the kingdom and brought its subterranean temples crashing down. Most Nerubians were killed and resurrected, the surviving nerubians hid deeper.
The remains of Muradin's dwarves, led by Baelgun Flamebeard conquered an entrance to the empire and founded the Doorward. When Illidan Stormrage used the Eye of Sargeras to destroy Icecrown, the earthquakes freed the Faceless ones, which took over a part of the kingdom. The nerubian survivors and the dwarves were mostly killed when Arthas went through the labyrinth to reach Icecrown Citadel. Arthas also destroyed most traps and treasures, which were still hidden there.
The Nerubians had a complex social organization, like ants or bees. The function of each individual was predetermined by genetics, as well by the subspecies they belonged to. The colonies were headed by a Nerubian queen who was responsible to giving birth to new Nerubians. The queens wielded great power, although in most cases they shared it with Spiderlords (a subspecies that bears more resemblance to beetles than to spiders, which are born from a litter of 20 egg sacks laid by a queen ) and the Nerubian viziers (another subspecies with preference for magic), acting as special advisors to their queen. There was also a Spiderlord reigning over all the Nerubians, and whose main function was coordinate the Nerubians colonies through its queens. He also should provide protection to them. All the spiderlords, and the last king of the Nerubians, Anub'arak, were killed and later resurrected by the Lich King after the War of the Spider, and they became Crypt lords of the Scourge. At the bottom of society were the Nerubian workers who performed various tasks. Workers who showed unusual physical abilities became warriors; workers who showed mental talents became seers, and those who demonstrated exceptional weaving skills became Nerubian webspinners.
The Lich King, the Eye of Sargeras and the death of the Forgotten one made most tunnels and buildings collapse, so only small parts are left. The former great empire is now inhabited by some surviving nerubians, undead minions of the Lich King, and some Faceless ones, which have recently been reinforced with Twilight's Hammer clan members.
- Doorward - entrance somewhere in Northrend
- Pit of Narjun - entrance in the Dragonblight
- Azjol-Nerub - the capital
- Upper Kingdom
- Shadow Web Caverns - somewhere on the way to Icecrown
- Icy Depths - beneath the Crusaders' Coliseum
- Naz'anak: The Forgotten Depths - beneath Icecrown