atris
atris is a Latin form of ater, meaning “black, dark; gloomy, deadly”. It is the ablative plural feminine adjective.
Found 65 times in the Latin texts on Socratos.
Where it is used
Vergil, Georgics 1.129: Ille malum virus serpentibus addidit atris
All forms of ater (declension table)
Source: Socratos (socratos.org), a free reader for Ancient Greek and Latin. Grammar from the Perseus Treebank and Morpheus; dictionary entries from Lewis & Short, A Latin Dictionary (Perseus Digital Library, CC BY-SA). Counts are from the texts on Socratos.