In Hindu religion, demons (asuras) are referred to as Daityas. They were the sons of Diti and Sage Kashyapa.
Diti served Sage Kashyapa with devotion to attain a valiant son. She was blessed with a child but Indra killed the embryo and cut into forty nine pieces and they became Maruts (a group of Devas).
Indra was the son of Aditi, another wife of Sage Kashyapa, and she did not like Diti’s son to be powerful and challenge Indra. So it was on her advice that Indra killed the son of Diti.
This cruel fate did not deter Diti from giving up, she continued serving Sage Kashyapa and she was blessed with two powerful sons, Hiranyaksha and Hiranyakashipu.
These two Daityas defeated Indra numerous times.