ekalavya is a well known character in mahAbhArata. Though he is mentioned comparatively minimally in the overall story, there is a specific sub-story that is very popular.
drONacharya is the guru of the pANdavAs and kauravAs - the royal princes of the kuru dynasty. When the caretaker of the kingdom - bhIshma - asks drONa to be the achArya for the princes and more specifically, train them in advanced warfare (sastra shAstra), as he was well known in that field. drONa readily agreed. During this time, two other people who were not part of the kuru clan, also requested drONa to be their teacher - one being karNa and the other being ekalavya. karNa was a close friend of duryodhana - the eldest son of king dhritarAshtra and ekalavya was the son of a nishAda king. drONa however refused to teach both of them saying that karNa was the son of a charioteer and ekalavya was the son of a nishaDa king (hunting tribe) and hence were not qualified.
Dejected but undeterred, ekalavya went back to his home place in the forest. There, he created an idol of drONa in clay and then, considering that clay idol to be his teacher, relentlessly practiced in front of it. By and by, he gained mastery of archery.
One day, the kuru princes came to the same forest area for playing along with their hunting dog. The dog strayed away from the group and came near where ekalavya was practicing archery and started barking, sensing another human being nearby. Ekalavya then shot a string of arrows towards the direction where the barking was coming from in such a way that the arrows shut the dog's mouth without harming it. Unable to bark anymore and surprised by the arrows, the dog ran back to the princes.
Upon seeing the dog with a set of arrows in its mouth, the princes were impressed with the skill of the archer and looked around. They came upon ekalavya and asked him if he was the archer and if so, how he became such a good archer. Ekalavya confirmed their suspicion and showed the idol of drONa and said he was drONa's disciple.
Surprised, they went back and narrated everything to drONa. arjuna, the favorite of drONa's disciples among the prices and the most skilled among all of them, told drONa that a promise drONa had made to him at the beginning of the tutelage that drONa will make arjuna the most skilled of all of his disciplies has been made false because ekalavya seemed to be a better archer than him.
Hearing this, drONa took the princes back to ekalavya. On seeing his guru, ekalavya fell at his feet and conveyed his gratitude of being his virtual teacher. drONa then told ekalavya that if he was truly his teacher, then ekalavya must pay the appropriate fees (guru dakshina) for having been taught. Happy to have been acknowledged, ekalavya pledged to provide whatever fees was asked of him by drONa, who then asked ekalavya for his right thumb. ekalavya readily agreed and cut off his thumb and handed it over to his guru, knowing well that the right thumb was essential to archery and without which he cannot be as effective as he was before.
The story as