Revenant

"We are slaves to a cycle of hatred. The undead curse brings us back to act to for our desires of vengeance, pain, and ruination. Vows meant to be fulfilled only after we have enacted suffering upon our enemies. We are brought back by the curse, and are only allowed to into the earth after we have sowed more hatred into this world." - Voice of the Silent King, to the mercenary Sahira before the battle of the four armies. 
Revenants are those who return from the dead due to oaths unfulfilled, injustices done, or revenge unfulfilled. They are creatures oathbound cursed never to find peace unless their acts go fulfilled. They vary in appearance from nearly spectral to rotting and decaying corpses. It is unknown how the undead curse returns these individuals but one common factor is that their existence will slowly annihilate their soul until their respective unfinished business is fulfilled. As such most revenants are aware of The Wheel more so than other races. When they close their eyes or meditate they can see a great slowly turning cosmic cog amongst a great void and often they are aware of the ticking clock upon their soul. 
Revenants are often called Orpheans after Orpheus, creator of the undead curse. This moniker comes with the associated disdain and fear towards the Breaker of the World. As such they find themselves mostly solitary, barely welcome into civilization and society due to the awe and fear witnessed by the people who see these walking corpses.