The paper presents the spectroscopic confirmation and characterization of the galaxy GHZ2/GLASS-z12 at redshift z = 12.34. This galaxy was identified through NIRCam photometry in GLASS-JWST ERS data, marking the first evidence of a large number of bright galaxies at z > 10. The NIRSpec PRISM spectrum reveals detections of several emission lines, including the O III Bowen fluorescence line at 3133 Å, which is the first such detection at high redshift. The prominent C IV line with an equivalent width of ~46 Å places GHZ2 in the category of extreme C IV emitters. The UV line-intensity ratios are compatible with both AGNs and star formation in a low-metallicity environment, with the low limit on the [Ne IV]/[N IV] ratio favoring a stellar origin of the ionizing photons. The galaxy is estimated to have a metallicity of ~0.1 Z/Z⊙, a high ionization parameter of log U > -2, a N/O abundance 4–5 times the solar value, and a subsolar C/O ratio similar to nitrogen-enhanced objects. GHZ2 is an ideal formation site for the progenitors of today's globular clusters, and its remarkable brightness makes it a "Rosetta stone" for understanding galaxy formation within 360 Myr after the Big Bang. The study highlights the importance of spectroscopic investigations to understand the physical conditions of early star-forming regions and the potential contribution of AGN accretion to the UV emission of distant galaxies. The results suggest that GHZ2 is likely a star-forming galaxy with low metallicity and high ionization parameter, and its properties are consistent with the formation of globular-cluster progenitors. The study provides insights into the physical conditions of high-redshift galaxies and the role of star formation in their evolution.The paper presents the spectroscopic confirmation and characterization of the galaxy GHZ2/GLASS-z12 at redshift z = 12.34. This galaxy was identified through NIRCam photometry in GLASS-JWST ERS data, marking the first evidence of a large number of bright galaxies at z > 10. The NIRSpec PRISM spectrum reveals detections of several emission lines, including the O III Bowen fluorescence line at 3133 Å, which is the first such detection at high redshift. The prominent C IV line with an equivalent width of ~46 Å places GHZ2 in the category of extreme C IV emitters. The UV line-intensity ratios are compatible with both AGNs and star formation in a low-metallicity environment, with the low limit on the [Ne IV]/[N IV] ratio favoring a stellar origin of the ionizing photons. The galaxy is estimated to have a metallicity of ~0.1 Z/Z⊙, a high ionization parameter of log U > -2, a N/O abundance 4–5 times the solar value, and a subsolar C/O ratio similar to nitrogen-enhanced objects. GHZ2 is an ideal formation site for the progenitors of today's globular clusters, and its remarkable brightness makes it a "Rosetta stone" for understanding galaxy formation within 360 Myr after the Big Bang. The study highlights the importance of spectroscopic investigations to understand the physical conditions of early star-forming regions and the potential contribution of AGN accretion to the UV emission of distant galaxies. The results suggest that GHZ2 is likely a star-forming galaxy with low metallicity and high ionization parameter, and its properties are consistent with the formation of globular-cluster progenitors. The study provides insights into the physical conditions of high-redshift galaxies and the role of star formation in their evolution.