The Olfactory trait marks effects that rely on smell to function. An olfactory effect can affect only creatures that can smell it; if a creature cannot perceive scents—because it lacks a sense of smell, is sealed in a suit, or is otherwise immune to odor—the olfactory portion of the effect does nothing to that creature.

This restriction applies only to the smell-based parts of an effect, as determined by the GM. A mixed effect (for example, an illusion providing sights, sounds, and smells) that gains the olfactory trait continues to affect a target through its other sensory channels, but any benefits or penalties that specifically depend on scent are ignored by creatures that cannot smell. Likewise, items or abilities that dull the senses can grant bonuses on saves against olfactory effects, while imposing penalties to smell-related Perception checks.

The trait appears on feats, hazards, spells, and items that weaponize, manipulate, or depend on scent: sour or rancid bombs that sicken, pheromonal messages that carry simple information, spells that lure creatures via enticing odors, or hazards like flower-traps whose stench or perfume exerts a mental pull. Equipment such as olfactory stimulators can grant or enhance a sense of smell, effectively broadening which olfactory effects can target the wearer and improving their ability to detect scent-based cues.