Cerbereus
Could not find Cerberei in Logeion dictionaries.
Cerberei Proper-name adjective: masculine vocative plural, Proper-name adjective: neuter genitive singular, Proper-name adjective: masculine nominative plural, Proper-name adjective: masculine genitive singular of Cerbereus
Cerbereumque canem nodat
Cerbereo dente teneor. qui dii mihi dent te!