Sanity
Typically used with: Psyche.
In short: don't go crazy. There are those possessed of spiritual fortitude strong enough to shrug off the bizarre, grotesque, and unnatural as though commonplace; souls who have hardened their minds against the unspeakable aspects of the universe.
The Sanity skill is a person's primary weapon against horrifying situations or unnerving supernatural oddities: extra-dimensional beings, mutilated corpses, visions of the end of the world, twisted scientific experiments, or reduced-calorie fast food. Anything which threatens to break a character's understanding of reality calls for a Sanity check.
Difficulty
The DL for horrifying phenomena is extremely varied. Your GM has the final call, as always, for determining DL for these.
Opposed Rolls
Sanity is rolled in response to Magic Spells and similar effects.