When Lord Krishna escaped to Gokul, the cowherds’ village across Yamuna River, Kamsa consulted his demon allies and friends, to find a solution and kill him secretly. He did not want to create suspicion in the minds of his people, or the Yadavs. He sent many of his friends in disguise and attempted to kill Krishna, but they never returned.
One day, he called Vatsasura, the demon who can take the form of a calf. This demonic calf form was not to be messed with. It might look like an innocent little calf, but can grow in size and strength at Vatsasura’s command. A hundred elephants would not match its strength. When he was ordered to kill Krishna, Vatsasura was very much delighted as he could go into Gokul, a village of cowherds, and wreck as he pleased.
Lord Krishna was playing near the bank of the river, and his friends first saw the calf. They wondered whom it belonged to, as they had never seen such an animal before in their herds. As one of them tried to catch the little calf, he was pushed down very hard. Then it challenged Krishna and his friends. As the friends were tricked by its small size, it charged at them, and made them run helter-skelter.
Krishna took up the challenge, and took the calf’s little horns. The calf grew suddenly and became a mammoth bull. It tried to push Lord Krishna and gore him, but Lord Krishna lifted the demon in that magic form, spun him overhead, and threw him high in the sky. The demon Vatsasura was dead before hitting the ground.