In the Ṛgveda we find a close parallel of Indra, though in a faded form, in Trita Āptya. He slays the three-headed son of Tvaṣṭṛ as does Indra; Indra impels him and he Indra, who is twice said to act for him. He is associated with the Maruts, but especially with soma, which he prepares; and this last feature associates him with Thrita in the Avesta, who was the "third man," as his name denotes, to prepare soma, the second being Āthwya. His slaying of the demon identifies him with the Thraētaona of the Avesta, who kills the three-headed, six-mouthed serpent, and he has a brother Dvita, "Second," while Thraētaona has two, who seek to slay him as in the Brāhmaṇas his brothers seek to murder Trita.[1] The parallelism points strongly to his identification with the lightning which is born among the waters, as his second name, Āptya ("Watery"), indicates; but he has been held to be a water-god, a storm-god, a deified healer, and the moon. In all likelihood much of his glory has been taken from him by the growth of Indra's greatness.
The lightning seems also to lie at the base of the deity Apāṁ Napāt, who likewise appears in the Avesta,[2] where he is a spirit of the waters, dwelling in their depths and said to have seized the brightness in the abysses of the ocean. He is also "Son of the Waters," born and nourished in them, but he shines and is golden, and is identified with Agni, who is often described as abiding in the waters of the air. The identification with a water-spirit pure and simple is, therefore, improbable, nor has he any clear lunar characteristics. Yet another form of the lightning is Mārariśvan ("He that Grows in his Mother"), the thunder-cloud. He is the messenger of Vivasvant and he brings Agni down to men, as the Prometheus of India; by friction he produces Agni for the homes of men. The lightning may likewise be represented by the "One-Footed Goat" (Aja Ekapād), which is occasionally mentioned among aerial deities, the goat symbolizing the swift movement of the flash and the single foot the one place of striking the earth, although this obscure god
