Brahmastra

In ancient Sanskrit writings, the Brahmastra (Sanskrit: ब्रह्‍मास्‍त्र, IAST: Brahmāstra) was a weapon created by Brahma. The Brahmashirsha astra and Brahmanda astra were similar weapons, created to be even more powerful.

As described in a number of Purana, it was considered as a very destructive weapon. It is said that when the Brahmastra was discharged, there was neither a counterattack nor a defense that could stop it, except by another Brahmastra, Brahmashirsha astra, or a Brahmanda astra. The Brahmastra never missed its mark and had to be used with very specific intent against an individual enemy or army, as the target would face complete annihilation. It was believed to be obtained by meditating upon the Lord Brahma, or from a Guru who knew the invocations. According to ancient Sanskrit writings, the Brahmastra is invoked by a key phrase or invocation that is bestowed upon the user when given this weapon. The user would have to display immense mental concentration. It could only be used once in a day.

Since Brahma is considered the Creator in Sanatana Dharma, it is believed by Hindus that Brahmastra was created by him for the purpose of upholding Dharma and Satya, to be used by anyone who wished to destroy an enemy who would also happen to be a part of his (Brahma's) creation. The target, when hit by Brahmastra, would be utterly destroyed.

The weapon was also believed to cause severe collateral damage. The land where the weapon was used became barren, and all life in and around that area ceased to exist. Both men and women became infertile. There was also a severe decrease in rainfall with the land developing cracks, as in a drought. The Brahmastra is mentioned in the epics and Vedas as a weapon of last resort and was never to be used in combat.

The Brahmastra, described in the Mahabharata, is a weapon which is said to be a single projectile charged with all the power of the universe.

...
Wikipedia