g-r vs z-W1 colour-colour plots for the eROSITA sample DR1_LS10_EXGAL_DET6P90 eROSITA DR1 sources (grey), detected also in Gaia (top left), Quaia (right left), and AllWISE/R90 (bottom left), respectively. The bottom right panel shows the distribution of the sources that are unique to eROSITA DR1. The sources in all panels are colour-coded as a function of redshift. Overlapped are the tracks of a few examples of typical SEDs, which show that many of the sources that are detected only by eROSITA are early-type and Seyfert 2 at redshift below 1.