Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
Lăchĕsis, is, f., = Λάχεσις, one of the three Fates: o duram Lachesin, Ov. Tr. 5, 10, 45; Sen. Apoc. 4, 1; Mart. 4, 54, 9; Juv. 3, 27; 9, 136; Claud. B. Gild. 203.