Counterpart and environment of J234402. Left: The optical counterpart of J234402. The yellow star represents the X-ray position and the yellow circle indicates the 1.0" (1σ radius) positional uncertainty of the eROSITA detection. This image was taken as an acquisition exposure with the Baade telescope using a white filter during our spectroscopic follow-up campaign. The source area includes four targets (labelled A–D), which were found to be at the same redshift. The Northern object, labelled A, is associated with the significant X-ray-flux increase detected by eROSITA, as well as with the significant optical outburst seen with Gaia (TNS#85552). Right: Overview of the spectra taken for the four objects that make up the galaxy group containing J234402. The labels A through D correspond to the objects in the image on the left. Object A is J234402. The spectra are plotted at their observed wavelengths, and the positions of several spectral lines, at z = 0.100 are shown in each plot. The plots illustrate the clear difference in spectral classification among the objects — object A shows an AGN-like spectrum, whereas the other three objects appear to be quiescent galaxies. The flux scale is arbitrary, and we note that the spectrum for object D has not been flux-calibrated. Spectra for A, B, and C are from the Baade (Magellan) observation. The spectrum for D is from the SALT observation of MJD 59206 (23 December).