Upper row: Evolution of the halo mass M_200, c with redshift z for all clusters in the Magneticum Box2 hr simulation, normalized to the final mass M_200, c(z = 0). The black line shows the median, with the dark shaded area marking the 1σ-bounds and the light shaded area marking the 2σ-bounds. The colored lines and their 1σ-bounds show the evolution of a subset of clusters split by their formation redshift (left) or their f_{ICL + BCG} (right) as given in the legend. Black dash-dotted vertical lines mark the redshifts at which the average cluster has accumulated 20%, 50%, and 90% of its total mass (horizontal black lines), marked by z₂₀, z₅₀, and z₉₀, respectively. We note that z₅₀ is what we define as formation redshift of a cluster. Lower row: Evolution of f_{ICL + BCG} with redshift z. As in the upper panel, the black line marks the average evolution of all clusters from Magneticum, with the gray shaded areas showing the 1σ- and 2σ-bounds. The colored lines and regions show the median and 1σ-bounds for the same subsets of galaxy clusters.