Salt

Salt is a common material with strong mystical associations, most notably of purity and cleansing.<ref>“Blake, salt is a purifying material, cleansing. It can work against certain Others,” Rose said. “There’s a ton in the study, if you can’t find any in the kitchen. Go and throw it at them!”</ref>

Uses

Impure ghosts which are tainted by anger and hatred (i.e. hostile ghosts) are vulnerable to salt,<ref>“Salt,” she said. “Is a pure substance, and any ghosts that actively want to hurt us are going to be naturally impure. Tainted by anger and hatred.” - excerpt from Damages 2.3</ref> as are Wraiths.<ref>“Salt,” I said.
“There’s salt on the road.”
“Salt holds power because it’s pure,” I said. “It was used to preserve. It held off rot and it stopped the emergence of life, if you salted the earth with it. It flavors food. Life, consumption, death, it fits into a niche in the cycle of life and death. Dirty, gritty salt, I don’t know how effective that’d be. Probably enough for something as weak as Molly is, but…” - excerpt] from Mala Fide 10.3</ref><ref name="14.5e1">“Ah, ow,” I said. Almost hurts. “Salt in eye.”
“Not a wraith,” Tiff muttered to herself, already digging through pockets I could make out Green Eyes swiping her claws at the thing. Touching only air. “Astral,” I said. [...] “Nightmare? No. Um. Doom. Curse made manifest? Roxanne, when you looted the bag, did you collect anything that looked like a dreamcatcher? A necklace, pendant, rosaries?” - excerpt from Sine Die 14.5</ref> Even a relatively nice ghost, such as Evan, is vulnerable to salt.<ref>“F-frostbite?” Evan asked.
He held up one hand, showing us fingers that were frayed at the tip. More ghostly than they might otherwise be.
“Salt,” I said. “This is all very deliberate.” - excerpt from Conviction 5.3</ref><ref>I was dimly aware as the dead bird was tossed at the side of the building. I felt it like a physical blow when salt was tossed onto the body. - excerpt from Conviction 5.4</ref> Malignant Others in general tend to be allergic to salt.

Unlike a Wraith, an astral being such as a Curse made manifest is not vulnerable to salt.<ref name="14.5e1"/>

Turtle Spirits, presumably because they are not impure, find salt neutral and it can be used to construct neutral bindings for them in the same way as chalk circles.<ref>Tortoise Spirits</ref>

References