The most fundamental of Hindu deities, is the Trinity of Brahma, Vishnu and Shiva - popular deities include Ganesha, Krishna, Hanuman and goddesses like Lakshmi, Durga,Saraswati.
Once all the creatures were created and their hunger satiated they began to reproduce. Soon there were too many of them. Brahma could see that the cosmos was choked with too much life. He wondered where he had made an error.
Saraswati pointed out to him that he had forgotten to create death.for life to go on he realised death was essential. He created Mrityu, He ordered her to go and kill all creatures. Mrityu was horrified of the formidable task and fled. Shiva found Mrityu crying in a desolate place. He consoled her and assured her that all those who would die would be reborn. So she would be mother even though she would kill. Thus it came to be that Death became not the end of life but a gateway to a new one. Mrityu took the form of Mahakali, devoured all life and Shiva became Mahakala, the lord of time, the regenerator. Life became a wheel, rotated by Shiva an eternal cycle of births and rebirths.