Once, the Asuras became undefeatable. They started to torture the inhabitants of Earth as well as the Devas. The Devas approached Lord Vishnu after being defeated by the Asuras. However, even Lord Vishnu was not able to supress the acts of the Asuras. To get a solution, Vishnu went to Mt.Kailas and started praying Lord Shiva. He worshiped by chanting the Sahasranama( thousand names) of Shiva.
He tossed a lotus at the ShivaLinga after chanting each name. To test Vishnu’s devotion, Shiva hid one of the lotuses Vishnu brought for the puja. At the end of the Sahasranama, Vishnu found that he was short of one lotus. He started searching for that flower. He couldn’t find it even after searching the whole world. Without being disheartened, Vishnu tossed one of his lotus-like eyes at the ShivaLinga to finish the puja. Lord Shiva became extremely pleased watching this. He appeared before Vishnu and asked.
“Sri Hari! I will grant your wish. Ask for anything.”
Vishnu replied, “Oh Lord! The Asuras are threatening the whole world. We are all in great anguish because of that. I don’t have enough weapons to face them.”
After hearing this, Lord Shiva gave Vishnu the SudarshanaChakra(the divine bladed disc) that he had.
Lord Vishnu thus successfully defeated the Asuras using this SudarshanaChakra.