A user's depiction of Spectral Sight.
Spectral Sight is a Demon hunter exclusive ability where they ritually blind themselves with the claw of a Demon (or a dagger, each case varies) so that they are enabled to see Demons and Undead with greater clarity.WC3MP 56 Illidan, being the first Demon Hunter, got his sight from Sargeras himself. Spectral Sight is comprised of a variety of dark and light shadings. Light reflects off of objects allowing the Demon Hunter to navigate unhindered. Beings (namely Fel Users and Demons) shine a radiant assortment of colors making them easy to detect even when disguised.
Notes[]
In World of Warcraft, players can get it by obtaining the [Cursed Vision of Sargeras]. Though this only allows the players to track Demons and Undead on their Mini-map.