Rudrani and Ruru
The goddess Rudrani was meditating in the Nilgiri hills. (Rudrani is again identified with Durga.)

There was a powerful demon named Ruru. He lived in a jewelled palace circled by the sea on all sides. Ruru performed very difficult tapasya and managed to please Brahma. Brahma then granted Ruru the boon that even after he died, his head would not fall down on the ground. Armed with the powers obtained from Brahma, Ruru set about oppressing the universe and conquering the three worlds of bhuloka, bhuvarloka and svarloka. He drover Indra out from his capital of Amaravati.

Ousted from heaven and scared out of their wits, Indra and the other gods went to the Nilgiri hills and began to pray to Rudrani.