Reaper Bolt Throwers

A deviation of the normal Elven Repeater Bolt Thrower, Reaper Bolt Throwers are used at sea to clear the decks of enemy vessels, and on land to scythe down ranks of enemy warriors. A mechanism of counterweights and cords allows the Reaper to shoot a hail of bolts, or a single missile with force enough to pierce a Dragon's hide. A Reaper's bolts are barbed and difficult to remove from the wounds they inflict. Those injured -- but not slain -- by such a shot often suffer such horrendous maiming on the bolt's removal that they are worthless as slaves, and are therefore left to bleed to death or given over to the bloody caresses of the Witch Elves.

Source
Warhammer Armies: Dark Elves (8th Edition) -- p. 39.