Son of Drona and Kripi. He was born with a jewel, Shirortana, on his forehead, that protected him.
Arjuna then chased him. Ashwatthaman aimed his weapon at the body of Uttara, the wife of Abhimanyu (Arjuna’s son), who was pregnant with her son Parikshit. Krishna took his Sudarshana Chakra, disabled Ashwatthaman’s weapon and saved Uttara’s unborn child. Krishna cursed him to have to go through the world alone, avoided by everyone, until the end of the Kali Yuga. He also took the jewel from him.
Ashwatthaman is a Chiranjivi, a infinitely long living being.
Ashwatthaman is included in this story about Drona
Read about Ashwatthaman as the last kaurava general here