Tribouet's Second Sight.
Second Sight is the ability used by hunters to identify the supernatural. This ability does not indicate another hunter as anything other than human unless they play their hand. This ability does not automatically reveal the true nature of the creature, just indicating it's supernatural.
Spirits or ghosts in the material world appear physical to the hunter. They may be obviously dead (burned, decayed or wounded) or look like perfectly normal people, but hunters can recognize they're not natural.
Spirits or beings that possess or hide within human hosts appear as images superimposed upon their human victims.
Beings that masquerade as humans or assume human appearance also register as not human, making the hunter feel a chill in their presence or the "person" shimmer strangely. A warlock may look completely normal, yet a hunter with this power active knows the person is wrong.
This ability also makes hunters immune to illusory powers. They can see through artificial hallucinations. Creatures trying to hide in plain sight become completely obvious. If a creature creates a false image, sound or other sensory illusion, it's clearly unreal to the hunter.
Waywards are incapable of turing off Second sight and are forced to see every supernatural creature.