A gigantic vaporous fog that resides in Shadar Logoth. It is the remnant of the hate and evil that destroyed City of Aridhol. It comes out at night and consumes any life that it touches. Only Shadar Logoth's other resident, Mordeth, is immune to it.
ACoS,Ch41 - As the Rand rescues Rand, Mashadar descends on them. They both use balefires on it causing it to retreat. Later, Mashadar claims Liah and Sammael.