κεἰς (keis)
κεἰς is an Ancient Greek form of ἐκεῖσε, meaning “to that place”. It is the adverb.
Found 45 times in the Ancient Greek texts on Socratos.
Where it is used
Apollonius Rhodius, Argonautica 1.1224: ὅσσαι κεῖσʼ ἐρατὸν νύμφαι ῥίον ἀμφενέμοντο,
Theocritus, Εἰδύλλια 15.74: κεἰς ὥρας κἤπειτα φίλʼ ἀνδρῶν ἐν καλῷ εἴης
Sophocles, Ichneutae 184: [Ο]ὐρίας Οὐρίας, αδ[]κεις
Source: Socratos (socratos.org), a free reader for Ancient Greek and Latin. Grammar from the Perseus Treebank and Morpheus; dictionary entries from Liddell-Scott-Jones, A Greek-English Lexicon (Perseus Digital Library, CC BY-SA). Counts are from the texts on Socratos.