Who Indra is
Indra is the hero of the Rigveda. About a quarter of its hymns are his, some two hundred and fifty of them, more than any other god receives. When the Vedic poets wanted to praise strength, they praised him.
He is a warrior and a king. He carries the vajra, the thunderbolt, which the divine craftsman Tvashtri made for him. Before a fight he drinks Soma, the pressed juice the poets offered to the gods, and he drinks great quantities of it. Then he goes out and does what nobody else can do.
His greatest deed is told again and again. A dragon named Vritra lay coiled on the mountain, holding back all the waters of the world. Indra struck him down, and the rivers ran free to the sea. For this the hymns call him Vritrahan, the slayer of Vritra. They credit him with much else besides. He propped up the sky and made the earth firm, and with his friends he broke open a cave of stolen cattle.
The poets tell him plainly what they want from him, which is cattle, sons, victory and rain. One hymn admits that some people doubted him. "They ask, where is he? They even say he does not exist." The poet answers with a list of his deeds and a refrain, "He, O men, is Indra."
His birth was as violent as his life. A strange and difficult hymn says he refused to be born in the ordinary way, was hidden away by his mother, and grew up alone.
He who killed the dragon and set the seven rivers flowing: he, O men, is Indra.