Wikipedia
In Finnish folklore, Ajatar (also spelled Aiatar, Ajattaro or Ajattara) is a spirit known as "Devil of the Woods". It is an evil female spirit that manifests as a snake or dragon. Ajatar is said to be the mother of the devil. She spreads disease and pestilence, any that look at her become ill, and she suckles serpents. Ajatar is related to the Lithuanian Aitvaras and the Estonian Äi, Äijo or Äijattar. She is in some ways similar to Babylonian Tiamat, dragon mother of the gods and goddesses.
The word "ajatar" is possibly derived from the verb ajattaa, "to make pursue", of Finnish word ajaa, "to pursue" (also: "to drive").
Also Swedish writer Astrid Lindgren pictured Ajatar in her book Ronia the Robber's Daughter. In the book they were dangerous flying creatures with women's heads.