What great mystical weapon was used by a non-god warrior in mythology, and what is the ability and power?

 An asur named Lavana pleased shiva through penance and obtained his Trisula(Trident), one of the most powerful weapons in entireity of Hindu mythology.

There was another powerful king named Mandhata who conquered whole earth in a single night,

There is nothing impossible of attainment by persons of virtuous behaviour. Mandhatri conquered the whole world in course of only one night,..

And he also vanquished Indra, lord of gods in combat. As well as conquered three worlds due to his might., ie bested gods, demons and humans of his era.

There the foremost of earthly kings, Mandhatri, vanquished Indra, the chief of the celestials.

However the same king along with his entire army was reduced to ashes when he faced Lavana and the latter used the Trisula against him.

Hurled by the illustrious deity, that weapon is competent to rive the entire Earth or dry up the waters of the ocean or annihilate the entire universe.

In days of yore, Yuvanaswa's son, king Mandhatri, that conqueror of the three worlds, possessed of imperial sway and endued with abundant energy, was, with all his troops, destroyed by means of that weapon.

Endued with great might and great energy and resembling Sakra himself in prowess, the king, O Govinda, was slain by the Rakshasa Lavana with the aid of this Sula which he had got from Siva.

Which was the most powerful weapon according to Hindu Mythology?

 The mystic sword named Asi should logically be the most powerful weapon in Hindu texts.

In the beginning of the universe brahma created a multitude of beings, of which some asuras always defied his rules and caused havok.

To destroy them, Brahma and the other sages conducted a thousand-year sacrifice, from which a divine being emerged out of the sacred fire. This being was then transformed into a mighty battle sword and given to Rudra, who used it to wipe out the asuras that were wreaking havok. The very fact that such a prolonged sacrifice was needed to forge this weapon shows that no existing weapon was powerful enough to accomplish the task.

And it looked exceedingly beautiful in consequence of the sacrificial plates and vessels all made of gold. All the foremost ones among the gods took their seats on it. The platform was further adorned with Sadasyas all of whom were high regenerate Rishis. I have heard from the.Rishis that soon something very awful occurred in that sacrifice.

It is heard that a creature sprang (from the sacrificial fire) scattering the flames around him, and whose splendour equalled that of the Moon himself when he rises in the firmament spangled with stars. His complexion was dark like that of.the petals of the blue lotus. His teeth were keen. His stomach was lean. His stature was tall. He seemed to be irresistible and possessed of exceeding energy. Upon the appearance of that being, the earth trembled. The Ocean became agitated with high billows and awful eddies.

Meteors foreboding great disasters shot through the sky. The branches of trees began to fall down. All the points of the compass became unquiet. Inauspicious winds began to blow. All creatures began to quake with fear every moment. Beholding that awful agitation of the universe and that Being sprung from the sacrificial fire, the Grandsire said these words unto the great Rishis, the gods, and the Gandharvas.

This Being was thought of by me. Possessed of great energy, his name is Asi (sword or scimitar). For the protection of the world and the destruction of the enemies of the gods, I have created him. That being then, abandoning the form he had first assumed, took the shape of a sword of great splendour, highly polished, sharp-edged, risen like the all-destructive Being at the end of the Yuga.

Then Brahman made over that sharp weapon to the blue-throated Rudra who has for the device on his banner the foremost of bulls, for enabling him to put down irreligion and sin. At this, the divine Rudra of immeasurable soul, praised by the great Rishis, took up that sword and assumed a different shape. Putting forth four arms, he became so tall that though standing on the earth he touched the very sun with his head.

Meaning this would be easily most powerful weapon. In Mahabharat era the sword was wielded by Drona, kripa and Nakula.

Is Gandiva a real weapon mentioned in the Mahabharata?

 Yes, Gandiva is a real weapon, as mentioned in the Mahabharata. It is a celestial bow of immense power, gifted to Arjuna by the fire god Agni during the Khandava forest episode. According to the epic, the Gandiva was created by Brahma, the creator, and had been passed down through various gods before being given to Arjuna.

Key Features of Gandiva:

1. Unmatched Strength and Power: The bow was unbreakable and produced a thunderous sound when drawn.
2. Immense Arrows Capacity: Gandiva came with an inexhaustible quiver of arrows.
3. Symbol of Prowess: It represented Arjuna's exceptional archery skills and divine favour.
4. Role in Kurukshetra: Arjuna used Gandiva throughout the Kurukshetra War, contributing significantly to the Pandavas' victory.

While Gandiva is a mythological weapon and not part of historical artefacts, its significance lies in its symbolic representation of divine support, courage, and skill in the Mahabharata.

Which weapon was more powerful, Narayanastra or Vaishnavastra?

 Vaishnavastra was More Powerful. Its one of the Strongest Celestial weapon along with Brahmashira and Pashupatastra.

Narayanastra was unique weapon. The more you resist, its Power would Increase again and again until it'll kill you.

But it has a serious Drawback., It won't attack Opponents who surrenders to The weapon.

When Ashwathama used Narayanastra, Krishna said to lay down all weapons and surrender in front of That weapon. Thus Narayanastra was Neutralised..

Vaishnavastra doens't have any such drawback. Krishna saved Arjuna from Bhagadatta's weapon. Clearly he was unable to save Himself even though Arjuna Boasted of countering it..

Having been thus pierced and pained, he angrily resorted to the vaishnava weapon. He invoked the mantra on his goad and hurled it towards Pandava’s chest. That weapon was capable of slaying everything and was released by Bhagadatta. Covering Partha, Keshava received it on his own chest. On Keshava’s chest, that weapon became the vaijayanti garland.

Even Krishna says you would've been Toast if I hadn't violated my pledge And Neutralised My weapon(Vaishnavastra).

It was from him that Pragjyotisha obtained this weapon of mine. O venerable one! There is no one in the worlds, not even Indra and Rudra, who cannot be killed by it. It is for your sake that I repulsed the weapon and violated my pledge. O Partha! The great asura has now lost his supreme weapon. Kill him, as I killed Naraka earlier, for the sake of welfare.

It has The Same Hype of Pashupatastra and Brahmashira…