Brahmastra was a weapon used by the ancient Hindus in war.
It is very powerful and it can not be countered.
There are two more Astras of this Kind.
The Paupatastra and the Narayanastra.
The Brahmastra has Lord Brahma as the presiding deity.
Pasupathastra Lord Shiva and the Narayanastra Lord Narayana.
As for as I read the texts, while there is no mention of Pasupathastra being fired except in One instance,
According to Kurma Puran, in the battle between the Purusha and demonic forces, Narasimha avatar escapes a powerful weapon called Pashupata.
It returned without causing any harm since it can be used only to uphold Dharma.
The Mantra for invoking the Pasupathastra was sealed by Lord Shiva to prevent misuse in Kaliyug.
This is the weapon of Lord Shiva and Kali.
Arjuna got this from Shiva and did not use it in the Mahabharata war.
Karna was cursed by Parashurama to the effect that he would forget the Invoking Mantra because he lied to Parashurama that he (Karna) was a Brahmin.
The Narayanastra was used by Aswathama in the Mahabharata war at Arjuna after Aswathama’s father Drona was killed.
The Narayanastra is also unstoppable.
Lord Krishna advised all those who were present to drop all their arms and prostrate before it.
They did so, it did not harm them and instead started destroying the Universe, because Aswathama did not know how to recall it.
Narada advised him to offer a target for it and Aswathama offered his Precious jewel on this head.
For this irresponsible act, Aswathama was cursed by Narada to become Immortal and be wandering in the forest alone.
What is the Mantra to invoke the Brahmastra?
It is the Gayatri Mantra, intoned in a specific way.
It is by altering the sound waves in the Ether that the Brahmastra got its potency.
Sound is referred to as the “Nada Brahma” or the divine sound, that is to say, in abstraction too there is a connection with the divine.
There are two types of sound: un-struck/un-heard sound and struck/heard sound.
Un-struck sound is a vibration of ether, the upper or purer air near the celestial realm.
The enlightened yogis seek the unstruck sound called “Anaahata Nada”, and only they can hear it.
The struck sound or “Aahata Nada”, is the vibration of air in the lower atmosphere closer to the earth.
It is any sound that we hear in nature or man-made sounds, musical, and non-musical.
So to release Brahmastra it’s the Anahata sound which is used to chant Gayatri and not the normal Aahata sound which we use for puja.
Stephen Knapp writes.
A key point in this regard is the ancient use of mantras, as already mentioned earlier. Not only could certain results be attained by the proper use of vibrations in sounds, but even today the use of particular mantras are known for calming the mind, lowering blood pressure, relieving one from unnecessary anxieties by changing one’s focus in life, and so on. It is also understood that certain mantras and prayers, such as the chanting of the spiritual names of God, bring to one the transcendental vibration of the spiritual world from where it comes. This means it is like a conductor, bringing the spiritual energy and frequencies that come from the transcendental strata. One of the classic mantras for this use is the Hare Krishna mantra (Hare Krishna, Hare Krishna, Krishna Krishna, Hare Hare / Hare Rama, Hare Rama, Rama Rama, Hare Hare). Experiments have already been performed that show the changes in those who regularly use this mantra. Plus, sages of India have used this mantra successfully for centuries in order to reach spiritual states of being.
Thus, by absorbing one’s consciousness in the sound vibration of these names of God, it will do several things, such as alter and improve the electrical impulses that are generated by the body, and help defend oneself from the negative impulses that one may encounter. In this way, it helps create a peaceful attitude within the individual and a healthier disposition. It also prepares one’s consciousness for perceiving higher levels of reality, opens one up to the spiritual world, gradually reveals one’s true spiritual identity, which would also allow one to see the unity between all people. It also harmonizes one’s existence with nature, and even begins to rekindle one’s real relationship with the Supreme Soul, God. Once the higher vibration of the spiritual realm is invoked on a regular basis in this way, and is opened for its use among the people in general, the chances for world change become enormous.
More on how sound can kill at Stephen Knapp’s site provided below.
Frequencies can kill. by Stephen Knapp