Vishnu, they say, is just one of a powerful threesome - the highest lords of the universe. However, though Brahma created the universe and Shiva can destroy it, it is up to the great god Vishnu to keep all creatures within well and happy.
When Vishnu returned to Vaikuntha after his Krishna avatar, Brahma, the creator, began to worry about the earth. Without Vishnu, he was afraid, chaos would ensue.
