Relations between the GRG projected proper length l_p and the host galaxy stellar mass M_⋆ (top panel) and between the GRG l_p and the host galaxy SMBH mass M_• (bottom panel). Our methods allow these properties to be determined for a small proportion of all literature GRGs only. Literature GRGs are marked with grey disks, and Alcyoneus is marked with a green star. Translucent ellipses indicate −1 to +1 standard deviation uncertainties. Alcyoneus’s host has a below-average stellar mass (percentile 25 ± 9%) and SMBH mass (percentile 23 ± 11%).