In Indian Mythology, all gods and goddesses have been depicted with a carrier or a ‘vahana’, which serves as a mount or a vehicle for the deity. Vah in Sanskrit means to carry or to transport.
Deities have always been depicted to have an animal or a bird as a vahana. This could be a real animal, or a mythological and sometimes even a combination of both.
In iconography, the vahana is both the symbol and the emblem of the deity that it carries. Nandi the bull, vahana of Shiva, represents strength and virility. Parvani the peacock, vahana of Skanda, represents splendour and majesty. The swan, mount of Saraswati, represents grace and beauty.
As the assistant of a deity, the vahana serves the function of doubling the deity’s powers. Durga the warrior destroys the demon Mahishasura with the aid of her mount, Manashthala the lion. Lakshmi, goddess of fortune, dispenses both material and spiritual riches from her mount, Uluka the owl. Ganesh, remover of obstacles, cannot go everywhere despite his elephant-like strength. However, his vahana, Mushika the mouse, can slide into the smallest crevices and overcome the greatest obstacles. He also carries Ganesh's benedictions.
The vahana symbolizes the evil forces over which the deity dominates. Mounted on Parvani, Skanda reins in the peacock's vanity. Seated on Mushika, Ganesh crushes useless thoughts, which multiply like rats in the dark. Shani, protector of property, has a raven in which he represses thieving tendencies. Under Shani's influence, the raven can make even malevolent events bring hope.
There are a number of smaller myths about each animal and its relation to the respective god and how they become their vahana.