Catalyzes the formation of (3R,6R,10S,11R,14R)-spiroviolene from geranylgeranyl diphosphate (GGPP) via a 1,11-cyclization and a 10Re,14Si-cyclization. (2E,6E,10E)-geranylgeranyl diphosphate = (-)-spiroviolene + diphosphate Binds 3 Mg(2+) ions per subunit. The Asp-Asp-Xaa-Xaa-Xaa-Asp (DDXXXD) and Asn-Xaa-Xaa-Xaa-Ser-Xaa-Xaa-Xaa-Glu (NSE) motifs are important for the catalytic activity, presumably through binding to Mg(2+). Belongs to the terpene synthase family.