The Witcher Bestiary - Nightwraith
Nightwraith Occurrence: Nightwraiths appear on fields and meadows; they can be found after dark, when the moon is high; they are specters but at the same time they maintain a strong connection with the natural world, they see the living but cannot understand them, because the dead cannot hear the living.

Immunity: Immune to blinding, poison, pain and bleeding attempts; they are fearless.

Susceptibility: Sensitive to silver and Specter Oil.

Tactics: They are able to grasp the moonlight and blind their enemies with it.

Alchemy: Death Dust, Shadow Dust, and ectoplasm.

Nightwraiths are born of moonlight, wind and the earth cooling after the heat of the day. They rise above the ground and whirl in a mad dance, which should not be seen by any mortal. If caught peeping, the mortal is blinded by moonlight, then taken into the circle and forced to dance until he expires, at times becoming a nightwraith himself.