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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-resolutionOptical SpecTrograph (GHOST) at the Gemini South telescope. The GHOSTspectrograph'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 inultra-faint dwarf systems, characterised by very low abundances ofneutron-capture elements (Sr, Ba, Eu), which are uncommon among stars in theMilky Way halo. Our analysis suggests that P180956 bears the chemical imprintsof a small number (2 or 4) of low-mass hypernovae ($\sim10-15 M_{\odot}$),which are needed to mostly reproduce the abundance pattern of thelight-elements (\eg [Si, Ti/Mg, Ca] $\sim0.6$), and one fast-rotatingintermediate-mass supernova ($\sim300\kms$, $\sim80-120 M_{\odot}$), which isthe main channel contributing to the high [Sr/Ba] ($\sim +1.2$). The smallpericentric ($\sim0.7$ kpc) and apocentric ($\sim13$ kpc) distances and itsorbit confined to the plane ($\lesssim 2$ kpc), indicate that this star waslikely accreted during the early Galactic assembly phase. Its chemo-dynamicalproperties suggest that P180956 formed in a system similar to an ultra-faintdwarf galaxy accreted either alone, as one of the low-mass building blocks ofthe proto-Galaxy, or as a satellite of Gaia-Sausage-Enceladus. The combinationof Gemini's large aperture with GHOST's high efficiency and broad spectralcoverage makes this new spectrograph one of the leading instruments fornear-field cosmology investigations.

GHOST Commissioning Science Results II: a very metal-poor star witnessing the early Galactic assembly