Using whatever magick they can to control it, the mages send it out to kill their enemies. In the past it has been sent after some powerful enemy or let loose to destroy whole villages or towns. It is important to understand that the Reaper is a near unstoppable force for death. It has, in historical times, decimated entire chantries. Physical barriers cannot stop it and only the most powerful or ancient of wards can keep it at bay.
Nothing can fly faster than it.
The strength of the Reaper depends upon the skill of the mages who created it and on where they performed the rote. Its strength is invariably vast however. The Reaper is a monstrosity and the spirits of which it is composed gradually fall away. Yet beyond a certain point, the Reaper begins to feed upon the spirits of those it murders, binding them into its own being. Many successes are required to create a Reaper.