All villages will have a fertility goddess. This goddess is believed to arise from the natural world itself and to be intrinsically linked to the ground of the village. She is a representation of the village itself, rather than simply a guardian figure. She often has the additional responsibility of overseeing rain, since, in the areas of South India east of the Western Ghats, the monsoon rains are the primary source of water for agriculture. She is the main protector of the village, especially against common diseases like smallpox or plague. Other goddesses preside over specific household objects, or act as guardians of cattle or children. Most of these deities are unique to their village and have their own origin stories, and many are worshipped only by members of a particular community. Mariamman is one of the most popular of this class of deity, worshipped throughout South India. She provides fertility and, in many places, protection against smallpox and other deadly diseases. Other popular goddesses include Pochamma in Telugu regions and Yellamma in northern Karnataka and western Telangana. Another common theme is the seven sisters, called "saptamatrikas" in Brahminical traditions. This collection of goddesses does not have a specific function, but may be called upon if a disease is affecting the family. In the area around Tirumala, it is said that these deities can be seen as young girls wandering around at noon, dusk or night. Village goddesses can have different personalities. Some are kindly, and will shower blessings on those who worship them. Others are vengeful and angry, and will unleash terror on the village unless they are propitiated. Many of these deities are especially worshipped by one particular community, for example Yellamma is worshipped especially by two Dalit communities: Malas and Madigas.