Mat Zemlya, also Matka Ziemia, and Mati Syra Zemlya (literally Damp Mother Earth), is the oldest deity in Slavic mythology, her identity later blended into that of Mokosh. She shares characteristics with Indo-Iranian Ardvi Sura Anahita “Humid Mother of the Earth.”
In the early Middle Ages, Mati Syra Zemlya was one of the most important deities in the Slavic world. Oaths were made binding by touching the Earth and sins were confessed into a hole in the Earth before death. She was worshipped in her natural form and was not given a human personage or likeness. Since the adoption of Christianity in all Slavic lands, she has been identified with Mary, the mother of Jesus.
An example of her importance is seen in this traditional invocation to Matka Ziema, made with a jar of hemp oil:
East – "Mother Earth, subdue every evil and unclean being so that he may not cast a spell on us nor do us any harm." West – "Mother Earth, engulf the unclean power in thy boiling pits, and in thy burning fires." South – "Mother Earth, calm the winds coming from the South and all bad weather. Calm the moving sands and whirlwinds." North – "Mother Earth, calm the North winds and clouds, subdue the snowstorms and the cold." The jar, which held the oil, is buried after each invocation and offering is made at each Quarter. (Slavonic mythology 1977:287)