As the vehicle falls upon its foes, arcane grenades made from captured Eldar wraithbone sow discord and terror within the enemy's ranks. It is fitted with a larger version of a Terrorfex, which can be fired instead of another of the vehicle's weapons in the Dark Eldar Shooting phase. It has the same effect as a Terrorfex except that is has an 18" range.
Horrorfex
Source: Codex: Dark Eldar (2002), p. 13