As his Guru-Dakshina (teacher's fee), Drona asked Ekalavya for his right thumb. Ekalavya, who had learned archery on his own by worshipping a clay statue of Drona, immediately cut off his right thumb and presented it to his guru. This cruel demand effectively ended Ekalavya's archery career, as the thumb is essential for holding a bowstring. Drona demanded this because he wanted to ensure that Arjuna would remain the greatest archer.