Story Behind "Karna"
Karna was the son of Kunti from the Sun God. The story is that Kunti, while still very young, had occasion to serve Rishi (sage) Durvasha. She looked after him with great dedication. Durvasha was highly pleased. He gave Kunti a mantra(chant) and said that whichever God she would think of after reciting the mantra, would appear before her and bless her with a son endowed with his own godly qualities.
Kunti got scared and wanted the Sun God to go away, but he pleaded his helplessness against the power of mantra. Surya however assured Kunti that even after being blessed with a son, she would still remain a virgin and would not have to suffer any opprobrium. And so Karna was born with kavach and kundal (armor which would make him invincible). Kunti was nevertheless afraid of social stigma and therefore she abandoned the child. She put Karna in a basket and placed the same in the Ganges river, the basket was seen by Adhirath, a charioteer, who had no issues. He picked up the baby and brought him up. That is why Karna is also sometimes referred to as Sarathiputra.
Kunti was later married to Maharaja(King) Pandu. One day when Pandu had gone for hunting, he killed a deer with an arrow. Actually, it was a Rishi who had taken the form of deer and was enjoying with his mate. The Rishi cursed Pandu that he would similarly die whenever he would mate with his wife. Maharaja Pandu thereupon retired to the forest and started living a life of abstinence. At this stage, Kunti confided in him the blessing given by Rishi Durvasha. Pandu exhorted her to use the mantras. That is how her other sons Yudhishthir, Bhim and Arjuna were born. (Nakul and Sahdeva were born off Madri).
Karna was keen to acquire the Brahmastra mantra from the great teacher Parshuram. However, he knew that Parshuram gave instructions to Brahmins (the priestly tribe) only. So he disguised as a Brahmin and beseeched Parshuram to accept him as a shishya(disciple). Parshuram accepted him as such and started giving him instructions. One day when Parshuram was resting in Karnas lap, it so happened that a bee stung Karna on the lower portion of his thigh. It was very painful and he started bleeding. However, fearing that if he moved his legs, he would awaken Parshuram, he did not move at all and continued to suffer. When Parshuram woke up, he saw Karna bleeding. He asked, Son, tell me truthfully who you are? A Brahmin cannot suffer so much physical pain. Only a kshattriya (the warrior tribe) can endure so much discomfort. Karna was obliged to disclose his identity. Parshuram was greatly annoyed because he was a sworn enemy of Kshattriyas. He therefore cursed Karna that as he had learnt through deceit, he shall forget the vidya (skill) which Parshuram had taught him at the crucial juncture.
Duryodhana and his 99 brothers were jealous and sworn enemies of their cousins, the Pandava brothers (King Panadava's sons). Meanwhile Duryodhan, the son of Pandus brother (and now king) Dhritrashtra patronised Karna and made him the king of Angadesh. Duryodhan, in fact, built him up as a counterweight to Arjuna. On the eve of the famous Mahabharata battle, Lord Indra, the rain God and king of heavens, disguised as an old Brahmin went to Karna and asked for his Kavach and Kundal in daan (donation). Indra was apprehensive that Karna, by virtue of his phenomenal skills as a warrior, may be able to overwhelm Arjuna. He therefore asked for this gift so as to reduce his strength. Karna had been cautioned by the Sun God that Lord Indra was going to make some such move. But Karna was so large hearted that he could not refuse anyone. Knowing fully well, that Indra was playing a trick on him disguised as a Brahmin, he yet parted with his Kavach and Kundal, which were parts of his body since birth and which made him invincible. Lord Indra was taken aback at Karna's capacity to give away anything asked for. He said, Karna, what you have done today, no ordinary mortal could have done. I am immensely pleased with your generosity. You can ask for any vardaan. Karna said, If you are really pleased with me, then you may kindly give me your weapon Shakti which has the potential to destroy any enemy. Lord Indra gave Shakti to Karna with the proviso however that he could use it only once and that thereafter the weapon shall return to him (Lord Indra).
Pashurams curse was to prove Karnas undoing. At the Kurukshetra battle, when face to face with Arjuna, Karna forgot the Brahmastra mantra taught to him by Parshuram. The wheels of his chariot sank in soft earth and he was immobilised. At that time, Arjuna defeated him. While Karna was on his deathbed, Lord Indra and Surya had a dispute regarding Karna's generosity and to settle the same they came disguised as beggars. Karna responded to the beggars by saying that he had nothing left to give, to which the beggars replied that he still had some gold in his tooth which would be valuable to them. On realizing that fact, Karna took a stone and broke the tooth with the gold and gave it to the beggars, epitomising the "way of life" he led.
That was the end of Karna, one of the greatest warriors of Mahabharata who was also the greatest daanveer. A man who would never refuse the request for any gift or donation, howsoever costly that might be and irrespective of the consequences of giving to his own well being or security.