Yarrow's effects can vary from subtle giddiness or mild mood alteration to euphoria (most often when made into a beer), this seems to be related to the thujone that some yarrow contains.
Historically, Yarrow was used by those consulting the I Ching, so it also has a long-standing reputation for aiding divination. Combined with mugwort (also containing thujone), Astral in Body makes for an exciting smoke for the more sensitive folx out there. Thujone is not appropriate for prolonged use (another reason for this smoke's seasonal availability).
Text, drive, and operate machinery with care with this smoke!