A novel polyphenolic natural product, galewone, with undescribed carbon skeleton, was isolated as a racemate from the culture of Daldinia eschscholzii IFB-TL01, a fungus obtained from the mantis (Tenodera aridifolia) gut. The galewone structure was elucidated by a combination of MS and NMR spectra, and substantiated by X-ray crystallographic diffraction. The absolute stereochemistry of each galewone enantiomers was determined by the CD spectrum. In compliance of the structural similarities, galewone might be the shunt products of the dalesconol biosynthetic pathway. Both (-)- and ( + )-galewones were evaluated to be anti-fibrotic against activated hepatic stellate cell line, CFSC-8B, with the IC50 values being 3.73 ± 0.21 and 10.10 ± 0.41 μM, respectively. Thus, galewone may serve as a starting molecule for the discovery of new anti-fibrotic drug.