Specifically mediates the conversion of oxidosqualene ((3S)-2,3-epoxy-2,3-dihydrosqualene) to achilleol B. Achilleol B is probably formed by cleavage of the 8-14 and 9-10 bonds of (3S)-2,3-epoxy-2,3-dihydrosqualene as part of the cyclization reaction, after formation of the oleanane skeleton. (S)-2,3-epoxysqualene = achilleol B Belongs to the terpene cyclase/mutase family.