Serine protease inhibitor that specifically inhibits clotting factor C (PubMed:8276848). Does not inhibit clotting factor B or proclotting enzyme (PubMed:8276848). Monomer (PubMed:8276848). Forms a covalent heterodimer with clotting factor C (PubMed:8276848). Interacts with big defensin (PubMed:8798603). Localizes in the large granules of hemocytes (By similarity). Secreted in hemolymph in response to external stimuli (By similarity). Expressed in hemocytes (at protein level). N-glycosylated. Belongs to the serpin family.