Today is Narak Chaturdashi. There are many significant incidents associated with this auspicious day in Indian lunisolar calendar.
In one of those events, Shri Krishna had killed the demon Narakasur today. Narakasur was one of the strongest kings in that era.
He was Ruling Pragjyotishpur near current day North West India.
Narakasur had kidnapped about 16,000 queens and Princes from all over India.
He had grown so much arrogant and demonic that he stole Earrings of Aditi, mother of deities.
This theft had strong symbolic meaning and was a great insult to the deities.
Shri Krishna was in a way son of Mata Aditi as he was Incarnation of Vaman.
So he was pledged to fight Narakasur and bring back the earrings.
He summoned Garuda and went to take on Narakasur along with his army single handedly.
He killed all the demon like Mur and others.
He got name Murari after that.
He not only retrieved the earrings of Mata Aditi but rescued the 16,000 princesses who were kidnapped by Demon.
Thus, We celebrate the day to remember that no matter how strong the evil is, it won't survive the Good.
Jai Shri Krishna.