My initial guess for the nature of the Messengers that Imbue the Hunters was that they were old Wraiths of great power or fragments of same that got across the Shroud after the start of the latest big Maelstrom.
- It all makes sense now. The reason the Messengers are so bent on getting the Hunters to fight the "Monsters" is revenge for the spirit-nuke and the whole Ravnos situation that created the Maelstrom in the first place, forcing the old Wraiths into a desperate fight for survival before Imbuing normal humans (the only group of people on the planet not involved with the whole mess).
- It Gets Worse. Hunters are slowly driven insane from the Hunt (when it does not kill them first). Which sounds alot like the survivors of the Ravnos Bloodline that all went insane upon Ravnos' death. Further Revenge or Irony on part of the Messengers?
There are no monsters.