Bestiary entry from the Clan Primer:
This creature always drops a trophy when it is defeated. This trophy is used in the Hunt Club side quest which involves trading in the trophies for items, armor and accessories.
|Common - (55%)||(Nothing)|
|Uncommon - (10%)||(Nothing)|
|Rare - (3%)||Soul Powder|
* Vorres is one of the more difficult Rare enemies to spawn. Head to the Hall of the Ivory Covenant in the Necrohol of Nabudis and lure one of the Dark Elemental enemies to the doorway that leads into the Cloister of Reason. This will cause the Vorres to spawn in the room to the south of the door.
Note that you need to have initiated the Hunt Club side quest for Vorres to appear.