(Max-Planck-Institute for extraterrestrial Physics, Garching, Germany)

Observational studies of distant X-ray luminous galaxy clusters can provide a direct view of the assembly phase of the most massive dark matter halos, the early thermodynamic history of the X-ray emitting hot intracluster medium, and the evolution of galaxy populations in the densest environments. In this talk, I will discuss the status of our ongoing efforts to find and study systems at z>0.8 within the XMM-Newton Distant Cluster Project (XDCP). This survey has compiled the largest sample of spectroscopically confirmed X-ray clusters to date, currently comprising 30 systems at 0.8≤z<1.6. I will present recent multi-wavelength observations of newly identified massive high-z clusters and will discuss the broad applications in cluster astrophysics and cosmology with a focus on the first implications for high-z X-ray scaling relations.