  Local Group (LG) very metal-poor massive stars are the best proxy for the
First Stars of the Universe and fundamental to modelling the evolution of early
galaxies. These stars may follow new evolutionary pathways restricted to very
low metallicities, such as chemically homogeneous evolution (CHE). However,
given the great distance leap needed to reach very metal-poor galaxies of the
LG and vicinity, no comprehensive spectroscopic studies have been carried out
at metallicities lower than the Small Magellanic Cloud (SMC, Z = 1/5
Z$_{\odot}$) until now. After five observing campaigns at the 10.4-m Gran
Telescopio Canarias, we have assembled a low-resolution (R $\sim$ 1000)
spectroscopic collection of more than 150 OB stars in the 1/10 Z$_{\odot}$
galaxy Sextans A, increasing by an order of magnitude the number of massive
stars known in this galaxy. The catalogue includes 38 BA-type supergiants, 4
red supergiants, and the first candidate 1/10 Z$_{\odot}$ binary systems, CHE
sources and systems hosting stripped stars. The sample massive stars mainly
overlap the higher concentrations of neutral gas of Sextans A. However, we find
some sources in low HI column-density regions. The colour-magnitude diagram of
the galaxy presents large dispersion, which suggests uneven, internal
extinction in Sextans A. This is the largest catalogue of OB-type stars ever
produced at sub-SMC metallicities. This sample constitutes a fundamental first
step to unveiling the evolutionary pathways and fates of very metal-poor
massive stars, analyzing the dependence of radiation-driven winds with
metallicity, and studying binary systems in an environment analogue to the
early Universe.
