The Zorya are Zorya Utrennyaya "Aurora of the Morning (who opens the gates to the celestial world when her father puts the sun forth)", goddess of dawn; Zorya Verchernyaya "Aurora of the Evening" (closes the gates), warrior goddess of dusk; and the goddess of midnight. They are possibly the fates. They watch the demonic god (with the form of a dog and can be called the "Doomsday Hound") chained to Ursa Major ("little bear" constelation); if he escapes the world will end.
Three little Zoryas:
pretty maidens,
dancing in the sky,
loving the dawn,
loving the earth.
Three little Zoryas:
their small hands
hold back the dog
of doom and darkness
as joy chains sadness.
Links for more Zorya and Related Information
Earthly Deities
Great Gods of the Slavs
Eastern European Folklore and Customs