Witch Elves

Witch Elves are the cruellest of all their heartless race, for they live only to serve Khaine's malevolent demands for bloody, agonising sacrifice. Their observances to the Lord of Murder are blood-slicked affairs. Still-beating hearts are ripped from victims' chests and hurled into fires, writhing flesh is daubed with gore-red runes and altars are decorated with the entrails of dying captives.

Yet ceremonies are but a part of the Witch Elves' worship -- their truest observances take place upon the field of battle. On the eve of war, Witch Elves drink blood laced with poisonous herbs, driving them into a divine frenzy. Whilst in this god-touched state, Witch Elves give no thought to their own defense, and seek only to hack foes apart in a blood-drenched orgy of slaughter. There is little grace to such an assault, merely a whirling storm of venom-coated blades that slash at the foe with maddened fury. Those enemies unfortunate enough to survive their wounds are rounded up by the Witch Elves at the battle's end. These poor souls are torn apart in wild victory celebrations, their blood offered in libation to the ever-thirsting Lord of Murder.

Source

 * Warhammer Armies: Dark Elves (8th Edition) -- p. 46.