There have been whispers of an organization known as the Claw of Shar, however, any details of their existence and abilities known by them are merely rumor. If they do actually exist, this might have something to do with them. Or maybe not. There is no guarantee of the accuracy or validity of anything below.
Nether Hands is believed to be an ability of the Claw of Shar.
By harnessing nether and focusing it around their hands while attacking, an assassin can employ powerful punch and claw attacks that will greatly increase damage potential.