Rig Veda to Purana - maintaining continuity - Part 2

So where from these gods Indra, Mitra Varuna came in Rig veda and what happened to them afterwards?

Swami Vivekananda provides the answer in a much more convincing way.

The spiritual knowledge of India and the Rishis also went through an evolution and the distinction of Sruti or revelations and smriti or book of customs have to be kept in mind. Puranas, Mahabharata, Ramayana etc. are smritis while Vedas are Srutis or revelations. SV says that in the beginning man looked upon nature with awe and reverence and tried to search for the supreme being in the natural and visible universe, in external nature. But after many futile searches they found that the macrocosm and microcosm are in reality the same. The supreme being who is in the nature is also within and thus arose the knowledge of Vedanta. So in the beginning forces of nature were looked upon as the manifestations of God's power through nature and thereby through them the Almighty Himself was worshipped. Indra, Mitra, Varuna and Ribhus were various names for the manifestations of the supreme cosmic power. They were not demigods themselves as scholars would like to believe. The Rig Vedic language is cryptic and Sri Aurobindo is of the opinion that through the hymns in Rig Veda the rishis actually implied the forces within and provided the means to propitiate them as manifestations of the supreme Self within. Like Vayu is being depicted as the praana which resides inside and controls the vital forces. Agni is not the fire burning outside but the fire of knowledge which leads to all other gods and to the supreme being, and so on. It may be that the rishis, like SV, came to know that there is actually no such border between external and internal nature and through the manifestation of external forces in nature they reached out for the self within which manifests as forces inside the body and mind. Indra is probably the king of gods, the mind and gods are the individual senses. This explanation is also found in some upanishadas. Also it is to be noted that in Gita chapter 10, Lord Krishna declares that He (the Supreme Being) is mind among all sense organs and Indra among all gods. This kind of equates Indra with mind and other gods with internal forces and senses. This is also in line with SV's explanation that rishi's at first looked outside and then they found that the same forces as outside reside inside and that self can be discovered within oneself through meditation. This was a grand discovery.

The Vedic karma kanda was meant for lesser mortals who were spiritually less developed as through work and sacrifices they could achieve the necessary purity for receiving the knowledge of supreme - as pointed out in Gita - all work (of sacrifices) ultimately leads to the supreme knowledge or jnana. Therefore as Swami Vivekananda preached, Karma leads to jnana, esp. if it is done without any desire. Even karma done with desire for heaven are better as they are but steps towards the grand ideals. This is an important aspect to understand before we move on to analyze the Puranas.