  This study focuses on Pristine$\_180956.78$$-$$294759.8$ (hereafter P180956,
$[Fe/H] =-1.95\pm0.02$), a star selected from the Pristine Inner Galaxy Survey
(PIGS), and followed-up with the recently commissioned Gemini High-resolution
Optical SpecTrograph (GHOST) at the Gemini South telescope. The GHOST
spectrograph's high efficiency in the blue spectral region ($3700-4800$~\AA)
enables the detection of elemental tracers of early supernovae (\eg Al, Mn, Sr,
Eu). The star exhibits chemical signatures resembling those found in
ultra-faint dwarf systems, characterised by very low abundances of
neutron-capture elements (Sr, Ba, Eu), which are uncommon among stars in the
Milky Way halo. Our analysis suggests that P180956 bears the chemical imprints
of a small number (2 or 4) of low-mass hypernovae ($\sim10-15 M_{\odot}$),
which are needed to mostly reproduce the abundance pattern of the
light-elements (\eg [Si, Ti/Mg, Ca] $\sim0.6$), and one fast-rotating
intermediate-mass supernova ($\sim300\kms$, $\sim80-120 M_{\odot}$), which is
the main channel contributing to the high [Sr/Ba] ($\sim +1.2$). The small
pericentric ($\sim0.7$ kpc) and apocentric ($\sim13$ kpc) distances and its
orbit confined to the plane ($\lesssim 2$ kpc), indicate that this star was
likely accreted during the early Galactic assembly phase. Its chemo-dynamical
properties suggest that P180956 formed in a system similar to an ultra-faint
dwarf galaxy accreted either alone, as one of the low-mass building blocks of
the proto-Galaxy, or as a satellite of Gaia-Sausage-Enceladus. The combination
of Gemini's large aperture with GHOST's high efficiency and broad spectral
coverage makes this new spectrograph one of the leading instruments for
near-field cosmology investigations.
