During the events of Diablo II: Lord of Destruction, the characters defeat the Prime Evil Baal, only to learn from Tyrael that the Worldstone had been corrupted and must be destroyed. The destruction of the Worldstone causes a shockwave so powerful it destroys the remainder of Baal's army, thus saving the Barbarian lands from its invasion. However, that same shockwave also destroys the Barbarians’ sacred Mount Arreat, causing a massive loss of morale amongst the Barbarian race.
With their main purpose for living stripped from them, the Barbarians scattered and left the destroyed Mount Arreat, becoming a nomadic race, wandering the lands of Sanctuary and pitching themselves in battle.
Since news of Diablo's re-emergence has spread, a small number of Barbarian warriors have begun roving the lands, preparing once again for war with the Prime Evils.
Female Barbarian concept art.
From the official writings of Abd al-Hazir:
“In my journey to catalogue the various denizens, civilizations, and fauna of our world, I have traveled far and wide, but never before have I been struck with such dismay as when standing upon the ramparts of the ancient fortress of Bastion's Keep. I came to see firsthand the barbarians, those near-legendary, immense, relentless, dual-wielding furies of combat dwelling upon their sacred Mount Arreat.
Instead, I stand here looking at a mountain that has been torn asunder by some extraordinary force. The sight, I must confess, is incomprehensible. Yet what I see before me cannot be denied.
What truly happened here? Where are those majestic warriors of old?
Though they were once misunderstood as simple, bloodthirsty invaders, the long and noble history of these proud people is now rightly acknowledged. And therein lies the greater tragedy here, for those of us familiar with the nobility of the barbarians remember too what they call their "vigil", the concept that lay at the very heart of their culture. The barbarians consider it their sworn duty to protect Mount Arreat and the mysterious object within. They believe that if they fail to uphold their duty to the great mount, or are not given a proper burial upon its slopes, they will be denied a true warrior's death, and their spirits shall roam the land without honor for all eternity.
If there are any barbarians left alive, they must truly be without hope. Perhaps this is the genesis of the rumors of monstrous things reported to resemble the barbarians in size and ferocity, but that are in reality nothing more than unreasoning, inhuman beasts. Could the destruction of not only their home but also their very beliefs have actually brought this magnificent race so low?”