An extreme form of Quickening; largely believed to be only myth. The Dark Quickening, generally disastrous and usually permanent, can change the Immortal in receiving one into a savage, heartless killer. In some cases, the victim might have their entire personality suppressed, and replaced by the compiled darkness of many 'evil' Quickenings. (Se: The Big Finish Audio Highlander The Pain Eater). Duncan MacLeod was the second after taking the head of Coltec, himself corrupted by a Dark Quickening, after having taken the head of the evil immortal, Kant in the episode, Something Wicked.