Mara – The Ancient Slavic Goddess of Winter and Death. She is the patroness of the winter, the underworld and symbol of the end of physical life as we mortals know it. Mara has many names: Marena, Morana, Mor, Morena, Marzanna and she is the all-powerful mistress of Winter, which covers the ground in icy shroud, so that it could rest and gain strength.
She is actually the Mother of all Slavs according to some interpretations. The father is Dazhdbog, god of the Sun, her polar opposite. She kidnapped him because she was in love, but he was due to be married with Zhiva, goddess of life. Thus their son was cursed to become a wolf and from him come all Slavs. (I believe that his name was Bogumir, but I'm too lazy to check).
Huh, I know Mara as basically the Buddhist equivalent of Satan who tried tempting Buddha into a life of debauchery, most infamously known by Shin Megami Tensei fans for being depicted as a green, tentacled penis monster riding a golden charriot.