In World of Warcraft's upcoming expansion, Battle for the Center of the Earth, the Nirubs form an alliance with the pioneer Saratas. But who are these Nirubs?How are they different from the Nirubs we met in Wrath of the Lich King?
Nirub HistoryThe Nirub are descendants of the Yaqui people, an insect-like creature that evolved from organic matter oozing from the ancient gods. The Yaki people further evolved into different races, and their evolution was guided by their ancient gods. The Nirub people, who settled in the north, were affected by their proximity to Yogsaron. Other Achians include Angela Worm, which evolved near Cthun, and Mantis Demon, which evolved near Asha. 
When the Lich King began to establish his power in Northrend, he found the Nirubs to be particularly difficult to deal with, as they were immune to control magic. In the ensuing Battle of the Spiders, the Lich King's army fought against the Nirubs, whose sprawling underground kingdom of Azor Nilub spread beneath the continent. Eventually, the Lich King won the war by invading and destroying their home, causing their home to collapse. While the Nirub are also immune to the undead plague, the Lich King is able to turn their corpses into undead creatures to serve as slaves in his army. Most of the Nirub we encounter in Wrath of the Lich King—like Anubrak, the last king of the Nirub people—are undead servants of the Lich King. However, not all Nirubi befell this fate. The Eldrainana Battle Guards, led by Killix, are still alive Nirub who survived the Battle of the Spiders and can be found in the Dragonbone Wilds. Some Nirubs even left Northrend. One of the possible destinations of the island expedition during the battle for Azeroth was the Flying Valley, a region inhabited by Volukar (Voru'Kar) – the island of the Nerubian who are still alive. Here, the Carapace item of Vorus Arak can be found - give it to Kilix the Dismantler, who can translate a story about Vorus Arak, a Nilub Swarm Lord who escaped the Spider War with his offspring by digging tunnels. The Nirubs in the Battle for the Center of the Earth
Like Volukar, the Nirub from Battle for the Center of the Earth are still alive and do not inhabit Northrend. Their kingdom – an area in Battle for the Center of the Earth – is known as Azkakhet, described by Blizzard as "the last kingdom of the Nirubs". The kingdom was ruled by Queen Ansurek, who was allied with Salatas. 
An interesting aspect of Saratas' relationship with these Nirubs is that she changed their evolution. This once again hints that Saratas may have been an Elder God - remember, it was the proximity to the Elder God that led to the evolution of the Yaqui into a different race, and the influence of Yogsaron created the Nirub. The Nirub of Azkakht are at war with the Alahis, the people of another region in the Battle for the Center of the Earth. It was this war that prompted Queen Ansurek to accept the dark "gift" of Salatas. Their capital – the City of Silk Threads – has been rebuilding on its own ruins for years. This led to the formation of class-based districts, with the richest Nirubs and the most favored by the queen living in the highest areas, while the poor and untrusted lived in the lowest. 
Under the guidance of Saratas, the Nirub are collecting the black blood of the Elder Gods, which, as far as we know, flows deep in the cracks of the world. Although it is easy to speculate, this information was collected for some "unknown purpose". The blood of the old gods is notorious for being powerful and deadly. Saron Evil Iron – an ore made from the blood of Yogsaron and found everywhere in Northrend – has the ability to corrupt anything it touches, and can convey the whispers of Yugsaron to those who encounter it. In the Azcros - Elder Gods timeline, visited during the Time Rift, the Rubble Tablet can be found, which describes a Hunger Games-like event that exists to please the "Ancients" – a creature previously only mentioned in Hearthstone. This creature has been described as the greatest creation of the Elder Gods and can be summoned by collecting enough blood. If the blood of the Ancients can bring this creature back to life, then perhaps the blood of the Old Gods can also be used to restore them. If that's the plan, then probably not all Nirubs will be happy to bring back their former masters they once refused. As it happens, like the Nirubs in Wrath of the Lich King, it seems that not all of them will be our enemies. A resistance force is fighting against Saratas and the Queen – and we can only assume that we will eventually help this force. 