Involved in the biosynthesis of beta-eudesmol, a sesquiterpene with antifungal activity and responsible for resistance of plants to ant attack. Produces mainly beta-eudesmol, but also smaller amounts of 10-epi-gamma-eudesmol, alpha-eudesmol and aristolene. (2E,6E)-farnesyl diphosphate + H2O = beta-eudesmol + diphosphate (2E,6E)-farnesyl diphosphate + H2O = 10-epi-gamma-eudesmol + diphosphate (2E,6E)-farnesyl diphosphate + H2O = alpha-eudesmol + diphosphate Binds 3 Mg(2+) or Mn(2+) ions per subunit. Secondary metabolite biosynthesis; terpenoid biosynthesis. Expressed in rhizomes. Detected in stems, but not in leaves. Peak of expression in summer. The Asp-Asp-Xaa-Xaa-Asp/Glu (DDXXD/E) motif is important for the catalytic activity, presumably through binding to Mg(2+). Belongs to the terpene synthase family.