The overall scientific driver of this project is to obtain the most sensitive view of the hard X-ray sky reaching the confusion limit in the 5–10 keV band and thus targeting a “new”, unexplored discovery space. We plan to fully exploit the XMM-Newton high-energy throughput and spectroscopic capabilities to characterize the X–ray spectral properties and cosmological evolution of accreting SMBHs. In particular, we aim at obtaining a fairly good census of the most heavily obscured and Compton Thick AGN responsible for the still unresolved fraction (∼ 50%) of the 5–10 keV background. Thanks to the excellent multiwavelength coverage in the CDFS, the role of obscured accretion in the context of galaxy evolution will be investigated with the best available data set.