One day there was a demon who transformed himself into a human and called out for lord shiva, shortly after lord shiva approached him and shiva said to the demon ask for anything you want so the demon responded saying “I want a boon that I would not be killed by any other human and that I shall live forever”.
Shiva granted the wish and then the demon transformed back into the original form of a demon. The five goddesses approached Parvati (also known as kali) mentioning that there has been a very big disaster is about to occur after telling Parvati they quickly went to slay the demon, the five goddesses chased after the demon the five goddesses fought the demon but the demon escaped and hid in a dead cow. The goddesses removed all their dirt from their bodies and dead skin and created a new avatar. After creating the goddess she went into the dead cow and fought the demon and ending the demons life.
Shortly after returning the goddess sought the five goddesses blessings but they refused as she was impure she approached lord shiva asking “what will I do now as I have killed a demon inside a dead animal”? Lord Shiva gave mother a blessing and stated from now on you will be named Meldi Maa you will have many devotees and you will be prayed and worshipped to in the kali yuga era anyone that will pray to you will be blessed.