Historically there was little difference between Asuras and Devatas during the times of Veda. Many of them were highly regarded, and comparable to necessary forces of nature. In post Vedic era especially in the narratives of Puranas many Asuras became synonymous with trouble makers, who come into conflict with Mahadev Shiva, Vishnu, Brahma and Indra wreaking havoc on civilizations. There are some famous Asuras-Devatas conflicts including Samudra Manthan regarding churning of the Ocean. There are some famous Asuras such as Vritra-Asur, Bana-Asur, and Bhasma-Asura who challenge Ādityas and specifically Indra, the king of Devatas.