Vijaya meaning victory. It was a divine weapon or bow. Vijaya was mainly wielded by LordParashurama who already had terrific skill. Later Parasurama gifted the bow to one of his disciples Karna.
Lord Shiva instructed Indra to give the bow to Parasurama for the task of combating the evil prevailing in the kshatriyas of the world. On 21 different occasions, when the ruling Kshatriyas began oppressing their subjects and committing sin, Parasurama - armed with the Vijaya bow - hunted them to the brink of extinction, nearly ridding the world of the kshatriyas. Each time, Parasurama donated the territory won from the kshatriyas to Brahmins for re-establishment of order.
How Karna got Vijaya
Parashurama takes Karna as his student, as told in the Mahabharata. Since Karna was a diligent and worthy student, Parashurama blessed Karna with the Vijaya along with other celestial weapons. Vijaya bow is clearly mentioned only once in Mahabharata, during the Kurukshetra war, on the 17th day, when he fought against Arjuna. After the death of Karna in the war, Vijaya is not mentioned in Mahabharata.
Features of the bow
The Sanskrit name Vijaya means Victory. This bow is said to give sure victory to the possessor. The string of this bow cannot be broken by any kind of astra or any divine weapon. Vijaya Dhanush is described in certain puranas having a dark colour with bluish hue. Every time an arrow is released from this bow, its twang is said to have produced reverberations akin to rumbling of charged clouds, causing terrible fear on enemies and produces flashes of light, brilliant as lightning, which blinds the enemy. This bow cannot be broken by any weapons or anyone and its so heavy that normal persons cannot even lift it. Every time an arrow is aimed, the energy of the arrow is amplified by multiple times as this bow is charged with sacred mantras. No weapon can harm a warrior who has Vijaya dhanush in his hand. Certain stories mention that the state of Kerala was produced from sea when Lord Parshuram shoot a divine arrow from his divine Vijaya bow, which is not true as Parashuram's primary weapon was Axe or Parashu. He hurled the axe at ocean and thus Varuna retreated to make it dryland for living.