The chemical abundances of Mg-poor star Gaia DR3 5731383034718059520 are indicative of an origin from a small accreted system or UFD. Minimal enhancement in α-elements and large depletion in r-process elements (Sr, Ba, Eu) are visible. Top: spectrum of the Mg b triplet for the star ([Fe/H] − 3.16  ±  0.09), with the strong Mg transitions marked in red. A comparison star of similar stellar parameters with Mg-normal abundance is plotted in blue. Bottom: measured elemental abundances.