Navratri 7th day Devi Kalratri
The sixth day of navratri is dedicated to the goddess kalratri, she is the a very dangerous manifestation of devi durga, even her name kalratri means the one who destroys the time, ignorance and darkness. According to Hindu mythology the origin story of this roop began when once two demons shumba and nishumba attacked heaven and discarded Indra and other gods out of it, which made them helpless and they started praying to goddess parvati to come and help them and restore the balance in the universe.
At the time when they invoked the goddess she was taking bath so did not went herself but created another goddess from within herself, this Devi was kalratri, as she reached to kill the demons shumba and nishumba, two other asura came as a hurdle in her way munda and chanda, to defeat them another goddess was formed as kaal roop kali and killed both the demon and since then she came to known as chamunda the slayer of chanda and munda.
Finally kalratri reached swargalok and began the battle that frightened whole of universe but goddess succeeded in killing the two and reestablished the rule of devas in swargalok. The appearance of the goddess is very frightening as she have black face along with four arms equipped with weapons.
Traditionally she is worshipped in the period of navratri that comes in chaitra and ashwin but she is also worshiped during the period of gupt navratri. Those who worship her are blessed with courage and become resolute in achieving their goals, the goddess removes all the hurdles and difficulties from there life and make them observe every happiness in this world and in the afterlife.