Enzyme of the diterpenoid metabolism involved in the biosynthesis of antibacterial oryzalides such as phytocassane (PubMed:21985968). Catalyzes the hydroxylation of ent-cassa-12,15-diene to form ent-3beta-hydroxycassa-12,15-dien-2-one (PubMed:25758958). ent-cassa-12,15-diene + 3 O2 + 3 reduced [NADPH--hemoprotein reductase] = ent-3beta-hydroxycassa-12,15-dien-2-one + 3 H(+) + 4 H2O + 3 oxidized [NADPH--hemoprotein reductase] kcat is 0.11 sec(-1) with ent-cassadiene as substrate. Belongs to the cytochrome P450 family.