He performed tapas for years and pleased Shiva, the lord of dhanurveda.
Shiva who was pleased with Viswaratha's severe penance appeared before him and said,"Son, I am Iswara, I am pleasedwith your tapas. Ask for any boon and you are going to have it" Viswaratha with folded hands said,"Grant me, O Bhagavan,the weapons to destroy Vasishta."Without a moment's thought Shiva said "Tatashu" and gave him several divine weapons.As he was blessed by Shiva all the devas came to the king, blessed him and said,"O king, from now onwards we will bewith you. Just call us and we will come and help you". The king was supremely happy and said, "If you consent, I willaccept you right now" They agreed. Viswaratha was glad to accept supremely powerful astras like chakra and pasha,and the terrible brahmastra. As he received those weapons he felt that he had abundant strength in him.
Immetiately he made for Vasishta's ashram. His latent hatred for Vasishta came to the surface. He reached the placein no time. He wrote on a bhurja leaf, stuck it to an arrow and shot it towards the ashram. The arrow fell at Vasishta'sfeet as if to pay respects to him. Vasishta took up the leaf and read it. On it was written, I am coming to destroy the ashram try to save yourself" It was signed by the king.
vasishta was unperturbed. He was called Vasishta because he had his intellect, reason and his indriyas under his control.The great sage was deep in meditation in front of his ashram. The king came and shouted, at him.
Vasishta opened his eyes and looked at Vishwaratha. He shot the divine arrow Pashupatha at the sage. The huts aroundbegan to burn. Birds came out of their nests screeching and the sages began to run helter-skelter in great fear.
Vasishta was cool. In a serious voice he said to the sages and other inmates of the ashram,"My dear people, don'tget disturbed. Be assured, not a single hair in the ashram is going to be hurt. I am going to save you" He gave thisassurance to his people. On the other hand Viswaratha thought that the very sight of Pashupatha would frighten Vasishtaand he would come, fall at his feet and beg pardon of him, but when he heard Vasishta's cool assurance to his people his hatred increased a hundered fold. He sent Santapanastra directly at Vashishta. On its way the divine astra burnttrees and plants. Viswaratha was sure that atleast then the sage would surrender to him and give him his cow Shabale.But to his displeasure and shock he heard a heart rending sound. He looked towards the spot where the sound came from.There was a strong, bright light engulfing the entire ashram. He was not sure whether the sound he heard or the light he saw was greater.
He saw the sage's Brahmadanda standing near the ashram for it's protection. It had the power of Vasishta's tapas in it. In an instant the king's arrow was swallowed by the Brahmadanda. Viswaratha was shocked. He felt that a hugecrocodile had swallowed it. He shot Vidhyadharastra at the sage. It met with the same fate. Then he sent taruna andkapalastra. They disappeared into the Brahmadanda. All the divine weapons he shot at the sage were swallowed by theBrahmadanda. Vasishta was unhurt. His weapons were reduced to insignificance. The king grew furious. He began tosend astras, chakras and pashas with divine force at Vasishta one after the other, but the Brahmadanda swallowedthem with ease as a whale would swallow small fish.
The king became desperate. He shot the all powerful agneyastra. The commanding deity of the astra was the god of fire.He was called Jwalamala because he could burn everything. Would he spare a small peice of dried wood, the Brahmadanda?Viswaratha's calculations went haywire.
The astra rushed towards Vasishta, but the Brahmadanda swallowed the astra with ease.
Viswaratha was at a loss to think of what to do next. Finally he had to shoot the invincible Brahmastra.By then, the Brahmadanda was in Vasishta's hand. The Brahmastra rushed at Vasishta vomitting fire and making a terrible noice.The sages watching the spectacle were filled with horror. They apprehended Vasishta's end. Even the devas in heavenwere shocked at the sight. The ashtra came and hit the Brahmadanda. It gave out a great streak of bright light. Toeveryone's surprice and releif the Brahmadanda swallowed the all poerful Brahmastra also.