air - a distinctive but intangible quality surrounding a person or thing; "an air of mystery"; "the house had a neglected air"; "an atmosphere of defeat pervaded the candidate's headquarters"; "the place had an aura of romance"
quality - an essential and distinguishing attribute of something or someone; "the quality of mercy is not strained"--Shakespeare
mystique - an aura of heightened value or interest or meaning surrounding a person or thing
note - a characteristic emotional quality; "it ended on a sour note"; "there was a note of gaiety in her manner"; "he detected a note of sarcasm"