VAJRĀYUDHA (Thunderbolt) The famous weapon of Indra.
1)
The making of this weapon. In olden days a fierce asura named Vṛtra was born. The Kālakeyas and many other asuras became his followers. They began to create havoc in the world, and cause harm to the Devas. At last under the leadership of Indra, the Devas went to Brahmā and informed him of their grievances and requested for advice as to the way of killing Vṛtra. Brahmā told them that only with a weapon made of the bone of the hermit Dadhīca, could Vṛtrāsura be killed. The Devas went to the bank of the river Śoṇa and saw the hermit Dadhīca, who was the foremost of munificent men, doing penance there. Indra told him the purpose of their visit. He told the Devas to take his bone, if it was useful to them. Saying this he forsook his body. The Devas took the bones of the hermit and gave them to Viśvakarmā who made a powerful weapon with them and gave that to Indra. They named the weapon the ‘thunderbolt.’
[M.B. Vana Parva, Chapter 100] .
2)
The face of Subrahmaṇya was cut. Once Indra was defeated by Narakāsura. He went to the Himālayas and hid himself there. Unable to see their King Indra, the devas went to Subrahmaṇya. When Indra knew this, he thought that Subrahmaṇya had taken possession of the world of the gods. So he came and fought with Subrahmaṇya. The thunderbolt of Indra touched the face of Subrahmaṇya and wounded him. From the blood which flowed from the face of Subrahmaṇya two noble men appeared who eventually became warriors of Subrahmaṇya.
[Kathāsaritsāgara, Lāvāṇakalambaka, Taraṅga 6] .
3)
Daily thunderbolt. In
[Viṣṇu Purāṇa, Aṁśa 1, Chapter 5 and Aṁśa 2, Chapter 8] , a process by which thunderbolt is made daily in the evening from the water particles thrown by Brahmins when they recite the spell Gāyatrī, is described. In the evening, the fierce giants called the Mandehas wish to eat the Sun. Prajāpati had given them a curse that though their bodies would not perish they would daily meet with death. So there is a fight between these giants and the sun daily in the evening. At that time the Brahmins recite the spell Gāyatrī with the Brahmapervading syllable ‘OM,’ and throw up water. This water becomes the Vajra weapon, and burns the giant.
4)
The thunderbolt became a tiger. The hermits Nārada and Parvata once went to the palace of the King Sṛñjaya. The King worshipped them and served them for a long time, as a result of which a son was born to him. Indra decided to lessen the superior power of these hermits. Once the son of the King, who was a mere boy, was playing in the forest. At the instruction of Indra, the thunderbold took the form of a tiger and went to the forest and killed the boy. Sṛñjaya became very sad. Nārada and Parvata brought the boy to lite again and gave him to the King.
[M.B. Śānti Parva, Chapter 30] .