Lord Indra is a storm god, wielder of the thunderbolt, Vajra, a weapon which he carries in his right hand. Like an Aryan warrior-king, he is fair complexion with ruddy or golden skin and rides a horse, or alternatively rides in a golden chariot drawn by two tawny horses with flowing manes and tails. He has a violent nature, an insatiable thirst for soma, an intoxicating drink which gives him his strength, and is a firm defender of gods and humans against Vritra, a demon who typifies the harsh aspect of nature, especially drought. As bringer of rain to a parched Indian countryside Indra was the most frequently invoked of the Vedic gods and the deity on which most of the early myths centered. The stories about his birth and his exploits as an infant make this devotion clear and explain in mythological terms Indra's rivalry to Varuna (which may be understood in terms of rivalry between the Brahmin priest caste and the Kshatriya warrior caste), his gradual assumption of many of Varuna's functions and virtues, and his eventual ousting of Varuna as chief of the gods.
Prithivi's attempts to conceal the birth of her son were ill-fated, for immediately the golden child Indra began to display that energy and impulsiveness which characterise him.
At the time of his birth humans were imploring the gods to come to their aid against the demon Vritra who had imprisoned the cloud-cattle, thus reducing them to starvation through drought. Hearing people crying out, 'Who will come to our aid?', Indra seized from Tvashtri the soma which they were offering to the gods and drank a huge quantity of it, worth a hundred cows. This drink fortified him to such an extent that he filled the two worlds. Seizing the thunder-bolt that had belonged to his father, Lord Indra set off in a chariot drawn by two horses to do battle against Vritra, accompanied by attendants and followers. Vritra roared as Indra approached, heaven shook and the gods retreated. Prithivi grew fearful for her son; but Indra was inspired by the great draught of soma and by the hymns of the priests on earth and was strengthened by the sacrifices; above all he possessed the thunderbolt, Vajra. He stormed and took Vritra's ninety-nine fortresses and then faced the demon himself. Though Vritra thought himself invulnerable, Lord Indra soon discovered his weak points and laid him low with the thunderbolt. Therewith the cloud-cattle were released and torrents of water flowed down to earth. According to some versions Indra repeats this heroic act at the end of every summer drought and thus re-establishes his strength in the eyes of mortals and gods.
But Indra hardly paused to hear the praises of the priests and of his fellow-gods. Scarcely born, he had seized the initiative as bringer of rain. In this act he had supplanted Varuna - though it must be admitted that he required much more effort to supply water than did Varuna. One interpretation of this shift of power relates to rivalry between Brahmin priests and Kshatriya warriors. His next act was to turn on his father (who is sometimes identified with Varuna). Seizing him by the ankle, he dashed him to the ground and killed him. His mother's plaints were of no avail: Indra had achieved his victory with the aid of his father's weapon so that in a sense his father performed the deed through him. But by killing Dyaus Lord Indra set the seal on his independence and full stature as a god; his murder of his father established his succession to him, just as his defeat of Vritra in part established his right of succession to Varuna's position of supremacy.
By his first heroic acts Lord Indra became king of the three worlds. Having acquired the air of life and the strength of soma, he gave them to others. He thus stands for the power of personal intervention, for the activity of the warrior, whereas Varuna stands for the inevitability of the cosmic order. While Varuna's strength is based on law and magic power, the source of Indra's strength is quite clear. It depends on the might of the god, supported by the offerings of mortals. Humans cannot understand the ways of Varuna, but by transferring allegiance to Indra they can hope to affect or even to direct the flow of divine benefits.
Indra is tireless in his opposition to demons. He repeatedly subdues Vritra, under whose leadership the Danavas were able to upset the eternal equipoise established between gods and demons, devas and asuras, good and evil, light and dark, and forces the Danavas to retreat to the ocean darkness. He also defends people and animals against the machinations of other demons. As bringer of rain, Indra already had some claim to worship as god of fertility; the following myth explains how he definitively captured that function from the other gods. At one point during the long struggle with the gods, the demons, counting on the fact that the gods derived much of their strength from people's sacrifices, decided to debilitate the gods by using poison and magic spells to defile the plants used by humans and beasts. They were so successful that people ceased to eat and beasts stopped grazing, and famine brought them near death. But the gods were equal to this challenge; they offered sacrifices and succeeded in ridding the plants of the poison. A great ceremony was held to celebrate this victory, at which offerings were to be made of the first plants to grow after the poison had been dispersed. However, a dispute arose as to which of the gods should be the first to receive this offering. It was decided that the matter should he settled by running a race. Indra and Agni won the race, and ever after Indra was regarded as a source of fertility - a role for which his parents, a bull and a cow, well fitted him.
Lord Indra gradually took over some of Varuna's other functions, and his role as fertility god extended to a new role as creator god. Like other Indian conceptions of the creator, however, Indra did not form the universe from the void but rather rearranged it, after taking possession. Thus, like Varuna, he used the sun as his instrument and measured out space; the six broad spaces which he noted included every existing thing. He then proceeded to build the universe like a house: he set up four corner posts and between them built the walls of the world; he thatched the house with the cloudy sky. The house had two large doors: the eastern was opened wide every morning to admit the sun; the western briefly every evening so that Indra could fling the sun out into the surrounding darkness. These doors were also used by the gods when they came to partake of sacrifices and libations. Indra maintained his creation by propping up the heavens, by maintaining the two worlds and the atmosphere, and by holding up the earth and stretching it. He was also the source of the major rivers.
Fortified with soma, Indra has the energy to regulate the heavens and the days, the months and the seasons. His love for and dependence upon soma are increasingly dwelt upon in the Vedas, but it is not until much later that this is regarded in any way as a weakness. In the Vedic age Indra is unquestionably the greatest of the gods, even though he may not be the object of such awe or fear as Varuna inspired at the time of his former glory. In the latter part of the Vedic period Indra became a more dignified, less active sovereign. He is pictured reigning in his heaven, Swarga, flanked by his queen, Indrani, and his advisers, the Vasus. Though still accompanied by a hunting dog (the dog was later to become an unclean animal), he has given up his horses, and his mount is a great white elephant called Airavata, which has four tusks and whose huge snowy bulk is likened to Mount Kailasa, where Shiva's heaven was to be.