Aśvatara(Aswatara) was one of the Nāga(s) (Naga; snake) born of the womb of Kadrū (Kadru), daughter of Dakṣa (Daksha). In Āstīkaparva (Astikaparva), while describing the names of snakes, his name is mentioned along with another Nāga called Kamvala– kamvalāśvatarau. In Mahābhārata (Mahabharata), and several Purāṇa(s) (Purana; Mythological Scripture), we have several mentions of Kamvala and Aśvatara together.

In Matsyapurāṇa(Matsyapurana) and Mārkaṇḍeyapurāṇa (Markandeyapurana), it is said that this Aśvatara lived in Prayāga (Prayaga). In Vanaparva of Mahābhārata, in the episode of Tīrthayātrā (Tirthayatra; journey to the sites of pilgrimage), we get the name of a tīrtha (site of pilgrimage)called Aśvatara tīrtha, located in Prayāga. The habitation of Aśvatara Nāga was probably known as Aśvatara tīrtha.

In the legend of Madālasā (Madalasa)and Kuvalayāśva (Kuvalayaswa) as described in Mārkaṇḍeyapurāṇa (Markandeyapurana), it is said that Kamvala and Aśvatara once pleased goddess Sarasvatī(Saraswati) by performing tapasyā (tapasya; penance), and wished that all the śruti of musical notes or mūrchanā come under their expertise. Out of concern for Kuvalayāśva, who was mourning his wife Madālasā, Aśvatara wished to brong her back, accepting her as his daughter. So he pleased Mahādeva through tapasyā.

In Sabhāparva of Mahābhārata it is said that Aśvatara was one of the distinguished Nāga(s) who reside in the court of Varuṇa and worship him.

In Udyogaparva of Mahābhārata, while Nārada describes the city of Bhogavatī to Mātali, he named Aśvatara as one of the distinguished Nāga(s) residing there.

In Skandapurāṇa it is described that Mahādeva used Aśvatara and Kamvala as his ear-decoration.

According to Bhāgavatapurāṇa (Bhagavatapurana) Aśvatara resides in the chariot of the sun in the month of Kārtika(Kartika) (according to Viṣṇupurāṇa, in the month of Fālguna)

According to Vāyupurāṇa (Vayupurana) and Brahmāṇḍapurāṇa (Brahmandapurana), Aśvatara was one of the distinguished Nāga(s) residing in the second plain of Pātāla (Patala; the underworld), called Sutala.

From Matsyapurāṇa (Matsyapurana) it is known that before the burning of Tripura, a chariot was jointly made for Mahādeva (Mahadeva), by Gods, Nāga(s) and Gandharva(s). Kamvala and Aśvatara were associated to that chariot, too.

From Viṣṇupurāṇa(Vishnupurana) it is known that this purāṇa was at first circulated in Nāgaloka (Nagaloka; abode of the Snakes). Vāsuki Nāga learned this purāṇa from Brahmā (Brahma), from Vāsuki, it came to Vatsa, from Vatsa, Aśvatara learned it, and from Aśvatara, Kamvala learned the same.