When Duryodhana saw that Ashwatthama's Narayana-astra had failed, he shouted, "Launch another! When they see the astra attack them a second time, they will take up their weapons and its fire will consume them."
"I cannot," said Ashwatthama sadly. "The Narayana-astra can be used only once. If I launch it again, the astra will turn back and attack us instead."
"But you must avenge your father's death!" said Duryodhana.
Ashwatthama nodded. "The Pandavas will pay," he vowed, his voice shaking with anger. "Before this war is over, I will make them pay in blood for taking my father from me."
Inspired by: Jaya: An Illustrated Retelling of the Mahabharata by Devdutt Pattanaik.
Notes: This story is on p. 257.