Hypomyces completus is a parasitic ascomycete in the order Hypocreales. The fungus grows on boletes, typically Suillus spraguei in North America, although the type collection was found on growing on in Siberia. The color of its subiculum (a crust-like growth of mycelium) ranges from white initially to yellow-brown to greenish-brown to brown to black; the fruitbodies (perithecia) range from pale brown to dark brown to black. Spores measure 35–40 by 4–6 μm.