Large-scale evolution of the A3391/95 analog found in the Magneticum simulation. The gas density distribution is shown in a cubic cutout region of 20 Mpc∕h per side around the redshift of the main system in comoving coordinates from redshift z ≈ 1 (left) to z ≈ 0.34 (middle) and z ≈ 0.07 (right). We note the clumps falling in along the large-scale filaments, merging with the main systems to form ever larger, denser, and hotter structures. The corresponding movie with more redshift snapshots is available online.