Ymirea teems with spirits, visible and invisible.
Although they have no bodies of gross matter, spirits are affected by sensory impressions. They do in particular seem to be affected by auditory and olfactory impressions.
Hence, choir song and other musical performances are common in temples, and bells and gongs may be carefully cast to ring with tones attractive or repugnant to different kinds of spirits.
Similarly, all spirits are affected by the smells of herbs and incense; Utukki in general and spirits of pestilence in particular seem to be attracted to gore and filth.
Werebeasts(?)