The Nerub'ar are undead nerubians who are attacking Warsong Hold.
They are invading Warsong Hold through the quarry within the stronghold. Unwilling to let them take down Warsong Hold's defenses Overlord Razgor sends Horde forces in going on the offensive against them. They've taken to storing their eggs scaffolding surrounding the Warsong Hold in order keep them away from the epicenter of conflict. Seeking to stop the attack on Warsong Hold Quartermaster Holgoth seeks to destroy the sinkholes that the Nerub'ar use as tunnels and passages within the quarry. The Nerub'ar forces attacking Warsong Hold ultimately retreated before the dedicated efforts of the Horde.
Nerub'ar found within the southern Geyser Fields come under attack by the Horde.
Nerub'ar forces can also be found within Icecrown Citadel.