Phase diagram of QCD in a magnetic background

We provide numerical evidence that the thermal QCD crossover turns into a first order transition in the presence of large enough magnetic background fields. The critical end point is found to be located between eB = 4 GeV^2 [where the pseudocritical temperature is Tc = 98 MeV] and eB = 9 GeV^2 [where the critical temperature is Tc = 63 MeV]. Results are based on the analysis of quark condensates and number susceptibilities, determined by lattice simulations of Nf =2 + 1 QCD at the physical point, discretized via rooted stout staggered fermions and a Symanzik tree level improved pure gauge action, adopting two different lattice spacings, a = 0.114 and 0.086 fm, for eB = 9 GeV^2 and three, a = 0.114, 0.086, and 0.057 fm, for eB = 4 GeV^2 . We also present preliminary results regarding the confining properties of the thermal theory, suggesting that they could change drastically going across the phase transition.