  Since 1990's the detection of extremely energetic air showers and precise
astronomical measurements have proved that our knowledge about fundamental laws
of Nature is far from being complete. These observations have found convincing
evidences against two popular believes: The spectrum of Cosmic Rays would have
a steep cutoff at energies around $10^{19}eV$ (GZK cutoff) and the
contravortial quantity called Cosmological Constant (dark energy) should be
strictly zero. They have been important additions to the yet unsolved mystery
of the nature of dark matter.For both phenomena many models have been
suggested. The top-down model decay of a Superheavy Dark Matter(SDM), also
called WIMPZILLA as the origin of the Ultra High Energy Cosmic Rays (UHECRs) -
is one of the most favorite candidates. Here we show that a meaningful
constraints on the mass, lifetime and cosmological contribution of SDM is
possible only if the energy dissipation of the remnants is precisely taken into
account. We discuss the simulation of relevant processes and their evolution in
the cosmological environment. We show that such a dark matter can be the
dominant component of Cold Dark Matter (CDM) with a relatively short lifetime.
Moreover, the equation of State of the Universe in this model fits the
Supernova type Ia data better than a stable dark matter. If a small fraction of
the mass of the SDM decays to an axion-like scalar field, its condensation can
also explain the dark energy without need for extreme fine tuning of the
parameters. Presumably, a meta-stable dark matter can explain 3 mysteries of
Physics and Cosmology. Finally we review some of the particle physics and
cosmological issues related to SDM and its associated quintessence field.
