A creature with this trait is a member of the fetchling ancestry. Fetchlings were once human, but generations of life in the Netherworld have transformed them.

Effects and magic items with this trait involve false sensory stimuli. Magic with the illusion trait creates false sensory stimuli. Sometimes illusions allow creatures a chance to disbelieve the spell, which lets the creature ignore the spell if it succeeds at doing so. This usually happens when a creature Seeks, Interacts, or otherwise spends actions to engage with the illusion, comparing the result of its Perception check (or another check or save the GM chooses) to the caster's spell DC. Mental illusions typically provide rules in the spell's description for disbelieving the effect (usually via a Will save).

If a creature engages with an illusion in a way that would prove it's not what it seems, the creature might know that an illusion is present, but it still can't ignore the illusion without successfully disbelieving it. Disbelieving a visual illusion makes it and those things it blocks seem hazy and indistinct, which might block vision enough to leave the other side concealed.

This magic comes from the occult tradition, calling upon bizarre and ephemeral mysteries. Anything with this trait is magical.

A creature with this trait is primarily constituted of or has a strong connection to occult magic.

Magic with this trait involves shadows or the energy of the Netherworld.

Planes with this trait are umbral with murky light. In the Netherworld, the radius of all light from light sources and the areas of light spells are halved.