A wraith, spectre (sometimes spelled specter), or revenant, is a being who has previously died only to be resurrected as an inhuman warrior and/or an evil spirit. Wraiths are not to be confused with the Undead, who are best described as living corpses. These beings wield powers associated with the Netherrealm: shadows and darkness for Noob Saibot and hellfire for Scorpion.
The best-known wraiths are Bi-Han and Hanzo Hasashi. Bi-Han had killed Hanzo as the elder Sub-Zero. Hanzo later returned as Scorpion and killed him out of revenge. Bi-Han then came back as the unholy Noob Saibot.
Smoke may be considered as a type of Wraith as well. In his Mortal Kombat (2011) ending, it was stated he was sacrificed to a demon, and returned to the mortal realm as an Enenra, a creature of smoke and vapor.
Freddy Krueger can also be considered a wraith, because he was once human and was brought back as an evil spirit by demons.