Diterpene synthase that catalyzes the formation of (-)-kolavenyl diphosphate from geranylgeranyl diphosphate (GGPP). (2E,6E,10E)-geranylgeranyl diphosphate = (-)-kolavenyl diphosphate Inhibited by high concentrations of magnesium. The Asp-Xaa-Asp-Asp (DXDD) motif is important for the catalytic activity through binding to Mg(2+). Belongs to the terpene synthase family. Tpsc subfamily.