Assessment of the rarity of the cosmosTNG volume. Specifically, we randomly place cosmosTNG subvolumes within the Millennium-I simulation, and measure the number density of halos with M_h > 10¹³ M_⊙. The probability density for many random subvolumes (blue) is contrasted against the same, but for volumes with a M_h > 10¹³ M_⊙ halo at the relative position of the zFIRE cluster within cosmosTNG (orange). The vertical red lines show the number density measured within the cosmosTNG variation runs, and the dashed line shows their mean.