Drona

Sage Bharadvaja fell in love with the apsara Gritachi. He closed his semen in a jar, in which Drona developed.

Parashurama taught him the art of war and he became the teacher of the Pandavas and Kauravas.

One of his goals was to get revenge on King Drupada, his childhood friend, who once promised him half his kingdom but then refused to do so. So he demanded as a fee from the Pandavas and Kauravas that they destroy Drupada.

He died by a lie of Yudhishthira; his son, Ashwatthaman, avenged him.

To read about Drona visit
http://hindumythologyforgennext.blogspot.com/2014/10/the-gurus-of-hastinapur-part-1.html