Every single Exorcist, registered or not, always brought a Spirit Talisman with them.
It was simply a matter of necessity.
A battle against strong Ghosts—with their Minor or Major Presence made it a requirement for Exorcists to always have a Spirit Talisman on them, or else it would be the same as putting themselves at a severe disadvantage going into the fight.
But another purpose for this was to prevent them from losing their sanity.
Mana descended from the intangible dimension.
It was alien to the tangible dimension, so there are side effects for native people to use it.
Exorcists who used that mana to fight Ghosts are putting themselves at an immense risk.
Excessive usage of mana would cause immense strain on the Exorcist's mind—and cause them to easily lose their sanity. Having an unstable mental state, like depression or even exhaustion, would also cause a similar effect.
Against a strong Ghost, an Exorcist would rapidly lose their sanity by simply being near it.
