  We present the XMM-Newton and the optical-VLT spectra along with the optical
and the near-infrared photometric data of one of the brightest X-ray (F(2-10
keV)~1e-13 erg/s cm^2) extremely red objects (R-K>=5) discovered so far. The
source, XBSJ0216-0435, belongs to the XMM-Newton Bright Serendipitous Survey
and it has extreme X-ray-to-optical (~220) and X-ray-to-near-infrared (~60)
flux ratios. Thanks to its brightness, the X-ray statistics are good enough for
an accurate spectral analysis by which the presence of an X-ray obscured
(NH>1e22 cm^-2) QSO (L(2-10 keV)=4e45 erg/s) is determined. A statistically
significant (~99%) excess around 2 keV in the observed-frame suggests the
presence of an emission line. By assuming that this feature corresponds to the
iron Kalpha line at 6.4 keV, a first estimate of the redshift of the source is
derived (z_x~2). The presence of a high redshift QSO2 has been finally
confirmed through dedicated VLT optical spectroscopic observations
(z_o=1.985+/-0.002). This result yields to an optical validation of a new X-ray
Line Emitting Object (XLEO) for which the redshift has been firstly derived
from the X-ray data. XBSJ0216-0435 can be considered one of the few examples of
X-ray obscured QSO2 at high redshift for which a detailed X-ray and optical
spectral analysis has been possible. The spectral energy distribution from
radio to X-rays is also presented. Finally from the near-infrared data the
luminosity and the stellar mass of the host galaxy has been estimated finding a
new example of the coexistence at high-z between massive galaxies and powerful
QSOs.
