  X-ray luminous clusters of galaxies at z~1 are emerging as major cosmological
probes and are fundamental tools to study the cosmic large-scale structure and
environmental effects of galaxy evolution at large look-back times. We present
details of the newly-discovered galaxy cluster XMMU J0104.4-0630 at z=0.947 and
a probable associated system in the LSS environment. The clusters were found in
a systematic study for high-redshift systems using deep archival XMM-Newton
data for the serendipitous detection and the X-ray analysis, complemented by
optical/NIR imaging observations and spectroscopy of the main cluster. We find
a well-evolved, intermediate luminosity cluster with Lx=(6.4+-1.3)x10^43 erg/s
(0.5-2.0 keV) and strong central 1.4 GHz radio emission. The cluster galaxy
population exhibits a pronounced transition toward bluer colors at
cluster-centric distances of 1-2 core radii, consistent with an age difference
of 1-2 Gyr for a single burst solar metallicity model. The second, less evolved
X-ray cluster at a projected distance of 6.4 arcmin (~3 Mpc) and a concordant
red-sequence color likely forms a cluster-cluster bridge with the main target
as part of its surrounding large-scale structure at z~0.95.
