Quietus is a Legendary Hand Crossbow for the Demon Hunter in Diablo III, obtained via purchase of Reaper of Souls Collector's Edition (or Digital Deluxe edition) as part of the Arma Mortis pack. It can only be used for Transmogrification.
Legendary Hand Crossbow
"I believe that just being in close proximity to the dark power within human souls induces an entropic effect in other materials. To be certain, though, I must test my theory by exposing material to the aura of the soulmetal I’ve forged and then inserting the exposed material into a living subject. A ranged weapon would make the ideal delivery system." — Author Unknown, Armis Mortem
- Quietus can be translated as "The End" or "Release" from Latin.