Probable tetrahydroxynaphthalene reductase; part of the gene cluster 29 that mediates the biosynthesis dihydroxynaphthalene (DHN)-melanin, a bluish-green pigment and a structural component of the conidial wall (PubMed:28818040). Catalyzes the NADPH-dependent reduction of 1,3,6,8-tetrahydroxynaphthalene (T4HN) into (+)-scytalone (By similarity). NADP(+) + scytalone = H(+) + NADPH + naphthalene-1,3,6,8-tetrol Pigment biosynthesis; melanin biosynthesis. Homotetramer. Belongs to the short-chain dehydrogenases/reductases (SDR) family.