According to Mahabharat, the son Dronacharya, Ashwatthama is an ansh Lord Shivas Kaal, krodh (anger) and Yam (death). During Samudra Manthan , Halahaal the fuming posion capable of burning universe appeared and all Dev Danav Manav Yaksha Gandharva fled. All of them along with Lord Vishnu and Lord Bramha came to Lord Shiva. Lord Shiva consumed Halahaal and held it in his throat. However unable to bear its consequences it started burning him.