  We present the multi-epoch monitoring with NuSTAR and XMM-Newton of NGC 1358,
a nearby Seyfert 2 galaxy whose properties made it a promising candidate X-ray
changing look AGN, i.e., a source whose column density could transition from
its 2017 Compton-thick (CT-, having line-of-sight Hydrogen column density
NH,los>10^24 cm^-2) state to a Compton-thin (NH,los<10^24 cm^-2) one. The
multi-epoch X-ray monitoring confirmed the presence of significant NH,los
variability over time-scales as short as weeks, and allowed us to confirm the
"changing look" nature of NGC 1358, which has most recently been observed in a
Compton-thin status. Multi-epoch monitoring with NuSTAR and XMM-Newton is
demonstrated to be highly effective in simultaneously constraining three
otherwise highly degenerate parameters: the torus average column density and
covering factor, and the inclination angle between the torus axis and the
observer. We find a tentative anti-correlation between column density and
luminosity, which can be understood in the framework of Chaotic Cold Accretion
clouds driving recursive AGN feedback. The monitoring campaign of NGC 1358 has
proven the efficiency of our newly developed method to select candidate
NH,los-variable, heavily obscured AGN, which we plan to soon extend to a larger
sample to better characterize the properties of the obscuring material
surrounding accreting supermassive black holes, as well as constrain AGN
feeding models.
