  In recent years, interstellar dust has become a crucial topic in the study of
the high and very high redshift Universe. Evidence points to the existence of
high dust masses in massive star forming galaxies already during the Epoch of
Reionization, potentially affecting the escape of ionising photons into the
intergalactic medium. Moreover, correctly estimating dust extinction at UV
wavelengths is essential for precise ultra-violet luminosity function (UVLF)
prediction and interpretation. In this paper, we investigate the impact of dust
on the observed properties of high redshift galaxies, and cosmic reionization.
To this end, we couple a physical model for dust production to the fully
coupled radiation-hydrodynamics cosmological simulation code RAMSES-CUDATON,
and perform a $16^3$, $2048^3$, simulation, that we call DUSTiER for DUST in
the Epoch of Reionization. It yields galaxies with dust masses and UV slopes
compatible with constraints at z $\geq 5$. We find that extinction has a
dramatic impact on the bright end of the UVLF, even as early as $\rm z=8$, and
our dusty UVLFs are in better agreement with observations than dust-less UVLFs.
The fraction of obscured star formation rises up to 45% at $\rm z=5$, in
agreement with some of the latest results from ALMA. Finally, we find that dust
reduces the escape of ionising photons from galaxies more massive than $10^{10}
M_\odot$ (brighter than $\approx -18$ MAB1600) by >10%, and possibly up to
80-90% for our most massive galaxies. Nevertheless, we find that the ionising
escape fraction is first and foremost set by neutral Hydrogen in galaxies, as
the latter produces transmissions up to 100 times smaller than through dust
alone.
