The Dark Reaper Warskin is used by the forces of Death. The Dark Reaper WS is similiar to Death's WS it just lacks the enchantments that Death's WS has. Unlike other WS the Dark Reaper WS does not use ranged weapon ( i.e. guns) it was designed for close combat and depends on it's cloaking field and noise dampeners to engage in melee combat. Seeing that most of Death's WS pilots are low-level War-Mages the sword has been designed to allow them to focus their powers (similiar to a Mages staff) and help them to direct their attacks. The Dark Reaper Warskins were created by the Techno-smiths of House Di ( Lord Death's true name).
The Cloaked Dagger Assassin used for scale.