The gods could not defeat the buffalo-demon
Mahisha. So they turned to Shiva
who advised all the deva
s to release their shaktis (spiritual prowess) locked within their bodies. The shakti
s of the gods emerged in female form – Shivani from Shiva
, Vaishnavi from Vishnu
, Brahmani from Brahma
, Aindri from Indra
, Kaumari from Kumara
. These goddesses fused together in blinding light
from which arose a magnificent goddess with many arms.
The gods called this goddess Durga, the invincible one. They armed her with their weapons – Varuna, the sea-god, gave her a rope; Indra, the god-king, gave her a thunderbolt; Vishnu gave her a discus; Kumara gave her a lance; Surya, the sun-god, gave her a bow and arrow; Chandra, the moon-god, gave her an axe; Yama, the god of death, gave her a mace; Brahma gave her a shield; Agni, the fire-god, gave her an axe; Vayu, the wind-god, gave her a conch; Shiva gave her a trident. Thus armed (ha!), Durga rode to the top of a mountain on a lion.
Attracted by her beauty, Mahisha came to the mountain and proposed marriage. "I will marry only he who defeats me in battle," said Durga. Mahisha immediately attacked the goddess. She hurled many weapons at the buffalo-demon but each time he rose unscathed. Finally she kicked him. Mahisha, immune to the weapons of the gods, succumbed to the touch of her feet. Durga immediately impaled him with her trident and blew her conch in victory.
All the gods saluted this warrior-goddess and celebrated her triumph.
Much info from hindumythology.com