Protease-inhibitor that contains multiple distinct protease inhibitor domains. Probably has serine protease- and metalloprotease- inhibitor activity. Inhibits the biological activity of mature myostatin, but not activin (By similarity). . This is the function of WFIKKN2 (WAP, follistatin/kazal, immunoglobulin, kunitz and netrin domain containing 2, ENSG00000173714).