Wikia

Taint was a Force power that allowed a Force-user to taint an object or person as it was the case after Grand Master Luke Skywalker fought Dark Lady of the Sith Lumiya and beheaded her leading to the dark side of the Force, thus causing Force-users connected to the light side to feel discomfort or even pain.^[1] The object or person would radiate the dark side to any Force-sensitives. If the being was neither of the dark side, or light side, and they came into contact with the object then it would cause them to suffer a stun effect. When the object was tainted, it caused all Force powers used against it to be more difficult to accomplish. Because of the nature of this power, it would cause beings to be seduced by the dark side.