|A Formless Foe|
"Brawn alone will not avail you against the likes of a phantom. Best you consider the vocation and skills of each member of your party afore engaging their kind."
As the objective states, five phantoms need to be defeated. Despite the location mentioned, any phantoms encountered and defeated count towards the total.
Numerable phantoms appear to the north of Gransys in the Deos Hills region at night time, near where Skeletons are likely to spawn. The Catacombs is another location where phantoms can be encountered.
Magic is a must. Bringing a Mage equipped with any elemental/enchantment spells, or equipping weapons that are permently enchanted on melee arisens and pawns will help greatly. A Mystic Knight with any of the Enchanter magick shield skills will work just as well.
After accepting the quest from the notice board in the Encampment, head to Gran Soren and sleep at the inn until night time. Travel to Conquest Road and surrounding the Old Garrison should be a number of phantoms. If there isn't enough there, head to the Healing Spring or towards Windbluff Tower as there are more than enough there to suffice.
Defeat the phantoms and the quest should complete.