Black Slayers are moredhel warriors who had renounced their mortality to become monsters with but one purpose: to kill for their master.
Once dead, the Black Slayers rise again to do their master’s bidding. Once risen from the dead, they may be halted only by magic means, by utterly destroying the body, or cutting the hearts from out of their bodies.
They had become a tool of Murmandamus, a leader who sought to emulate the vanished Valheru and bring all the world under his dominion. It was he who had gathered the moredhel under his banner and who had given rise to the abomination that was the Black Slayers.