I heard in a video Ekalavya was killed by Lord Krishna and at that time Lord Krishna gave a boon. i e. rebirth as Dhrishtadyumna to take revenge on Dronacharya. Is that true?
According to Mahabharata, Adi Parva, SECTION LXVII, Dhrishtadyumna was incarnated from the portion of Agni.
"Know also, O monarch, that the mighty car-warrior Dhrishtadyumna was a portion of Agni.
And Ekalavya was incarnated from the portion of Asura called Krodhavasa.
Madraka, and Karnaveshta, Siddhartha, and also Kitaka; Suvira, and Suvahu, and Mahavira, and also Valhika, Kratha, Vichitra, Suratha, and the handsome king Nila; and Chiravasa, and Bhumipala; and Dantavakra, and he who was called Durjaya; that tiger amongst kings named Rukmi; and king Janamejaya, Ashada, and Vayuvega, and also Bhuritejas; Ekalavya, and Sumitra, Vatadhana, and also Gomukha; the tribe of kings called the Karushakas, and also Khemadhurti; Srutayu, and Udvaha, and also Vrihatsena; Kshema, Ugratirtha, the king of the Kalingas; and Matimat, and he was known as king Iswara; these first of kings were all born of the Asura class called Krodhavasa.