  This overview article describes the legacy prospect and discovery potential
of the Dark Energy Survey (DES) beyond cosmological studies, illustrating it
with examples from the DES early data. DES is using a wide-field camera (DECam)
on the 4m Blanco Telescope in Chile to image 5000 sq deg of the sky in five
filters (grizY). By its completion the survey is expected to have generated a
catalogue of 300 million galaxies with photometric redshifts and 100 million
stars. In addition, a time-domain survey search over 27 sq deg is expected to
yield a sample of thousands of Type Ia supernovae and other transients. The
main goals of DES are to characterise dark energy and dark matter, and to test
alternative models of gravity; these goals will be pursued by studying large
scale structure, cluster counts, weak gravitational lensing and Type Ia
supernovae. However, DES also provides a rich data set which allows us to study
many other aspects of astrophysics. In this paper we focus on additional
science with DES, emphasizing areas where the survey makes a difference with
respect to other current surveys. The paper illustrates, using early data (from
`Science Verification', and from the first, second and third seasons of
observations), what DES can tell us about the solar system, the Milky Way,
galaxy evolution, quasars, and other topics. In addition, we show that if the
cosmological model is assumed to be Lambda+ Cold Dark Matter (LCDM) then
important astrophysics can be deduced from the primary DES probes. Highlights
from DES early data include the discovery of 34 Trans Neptunian Objects, 17
dwarf satellites of the Milky Way, one published z > 6 quasar (and more
confirmed) and two published superluminous supernovae (and more confirmed).
