Mahakali

Kali is the avatar where parvati, the shakti merges with shiva, the rudra or destroyer and attains victory over negativity. This negativity is often not external. Over the years the myths and folklore has made a more black and white version of Kali's triumph over asura. Asura is opposite of sura, which is positive energy, nature spirits. Asura is therefore the negative or evil spirits causing disharmony. Kali over generations and in different mythos has been narrated as an avatar of durga who appears in Rudra or bhayankar form (ferocious, fiery, the roarer). She slays heads and drinks the blood, performs tandav (fiery dance) on the fire which can destroy the earth. Shiva lays down at this point and asks Kali to perform the dance over him to save the earth from being destroyed. Kali in her rudra form doesn't recognise shiva, steps on his body and gains consciousness. She hangs her tongue out in lajja(shameful). It's our conscious mind that needs the courage to slay the negativity that resides in us but at the same time to find peace and gratitude to not destroy ourselves in the process of discarding our negativity.