Āḍi (Adi)is a terrible dānava (danava; demon). According to Skandapurāṇa (Skandapurana), Āndhakāsura(Andhakasura) is the uncle of Āḍi. However, Matsyapurāṇa (Matsyapurana) refers to Āḍi as being the son of Andhakāsura, who was slain by Śiva (Siva). In order to take revenge, Āḍi started performing a great tapasyā (ascetic practice). Pleased by his tapasyā, when Brahmā wished to give him a boon, Āḍi demanded that he should be granted amaratva (amaratwa; immortallity). Brahmā said that this was not possible. Then Āḍi wished that he would die only when he would undergo a change of his self. Brahmā granted this.
At that time, Śiva came to practice his tapasyā (tapasya) in Mandaraparvata, separated from Umā-Pārvatī (Uma-Parvati). Āḍi, learning this, assumed the guise of a snake. He escaped the vigilance of Vīraka (Viraka), follower of Śiva and entered into his abode. There, assuming the guise of Umā, he created sharp teeth in the vagina of his assumed self. Then he sought an union with God Śiva, who understood everything. He then applied Raudrāstra (Raudrastra; the weapon of Rudra) to his phallus and got united with the disguised Āḍi, and the dānava died immediately.