The martial teacher (guru) to both the Pandavas and the Kauravas, whose own sense of duty as a warrior ultimately outweighs his affection for his most gifted student.
महाभारत · Mahabharata
A master of advanced weaponry, Drona trains the Kuru princes together at Hastinapura, openly favoring Arjuna as his finest pupil while declining to formally teach the tribal prince Ekalavya, who then masters archery alone by practicing before a clay image of Drona — a story often read today as an example of the era's exclusionary access to formal learning.
Bound by loyalty to the Kuru throne rather than personal preference, Drona commands the Kaurava army after Bhishma falls, and is killed only when Yudhishthira's ambiguous statement about Ashwatthama's death convinces him, falsely, that his own son has died — a moment the epic treats as morally costly for the Pandavas even in a war fought for a just cause.