Аннотация:4MOST-ChANGES will target a legacy sample of active galactic nuclei (AGN), based on optical continuum variability and spectral energy distribution (SED) selection from several existing sur- veys, and ultimately complemented by Rubin LSST to: 1) constrain the low-MBH, low-L/LEdd end of the accretion and black hole (BH) density functions to z ~ 1, and, by extension, BH seed models; 2) investigate correlations among AGN (MBH, L/LEdd, ultraviolet slope, outflows, variability) and host properties (stellar age, metallicity, kinematics); 3) confirm/characterise rare BH subsamples (extreme variability, tidal disruption events, lensed, intervening absorption line systems) for detailed multi-wavelength follow-up studies.