Argento is a star, mentioned in the first book, that was on Sophie's list for her star bottling assignment. It has a metallic-toned light, and was much more difficult to find on any star on Dex's list, causing Sophie to strain her memory looking for it. It is unknown what color it emits, though when seeing all the bottles lined up Sophie notes that they were silver, gold, black, white, copper, and green. Along with Auriferria, Pennisi, Merkariron, Styggis, and Achromian two lines are formed pointing at Elementine.

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