Ezrohir

Although the Zeraphi finally recognized the dangers of Ember and gave up their war over the Estherians' Ember, one faction refused to lay down arms. The Ezrohir pursued the retreating Estherians, seizing their mines. With the Estherians' Ember, the Ezrohir eventually perfected their own process for encasing souls in suits of armor.

But the process was flawed. The Ezrohir gained immortality - but the corrupted ore burns out over time, and the Ezrohir die unless they can procure more Ember. Their insatiable need for Ember led to a disastrous war with the Zeraphi, and the Ezrohir were driven out into the Mana Wastes, forced to hide in their ancient fortresses. For centuries they have waited, and plotted ... and their vengeance is finally at hand.

Source

 * Official Torchlight 2 site