A state of delusion and fury afflicting those who've been touched by The Darkness; people severely afflicted are also known as The Lost.
Exposure can occur in varying degrees. A mild case of night sickness may show symptoms of unease, shaking, twitching, and loss of memory or cognition with onset hallucinations. These often subside over a period of days. More moderate cases may leave victims in a crazed state with suicidal tendencies. In severe cases, the victim is no longer human, as all remnants of humanity are lost. Their mind gone, The Lost revert to basic animalistic behaviors for survival.
Oddly, night sickness only seems to afflict humans, as other races only suffer the temporary effects of daze and memory loss.
There is yet no known cure.