There was a question “Is that the reason why the Veda samhitas have absence of some key devas and deities like Ganesh , Kali , mahavidyas , avatars of Vishnu. They have been lost or is it by design that rishis want us to explore them via indra?” and the answer became too long so posted it as a post. 

A simple question and here is a longish answer.

First a bit about Sanskrit, the language in which all these texts, Ved, Vednant, Puran etc are written. One thing you have to remember is that Sanskrit, Devbhasha Samskrutam has no proper nouns. Am sure this sounds odd to you. So, a brief explanation,

Eg This sentence, ‘I am Samantha’. In this sentence ‘Samantha’ is a proper noun. It is a girl’s name and by this sentence you understand that I am a girl named ‘Samantha’. The word Samantha has no meaning in itself. Thus it is a proper noun. That is the end of it, no more meanings here.

Eg This sentence ‘I am Manish’. Here Manish is a Sanskrit word. It has a meaning in itself. Every word in Sanskrit has a meaning. Every word can be used as an adjective to describe something. If you think of ‘Manish’ as a noun, then you will understand that I am boy named ‘Manish’. But if you think of ‘Manish’ as an adjective then you will think that I am ‘someone who can be described as Manish’. There is a very big difference in these two levels of understanding. The Sanskrit word ‘Manish’ is a samas/ compound word, it is expanded to ‘Mansaya Isha iti Manish’. The simplest translation of this compound word would be ‘the Highest God of the Mind is Manish’. So our sentence ‘I am Manish’ completely changes its meaning depending on ‘Manish’ being understood as a proper noun or adjective.

Sanskrit is a highly esoteric language, it has layers of meanings. Understanding it depends on the capacity of the person who is reading it. Enlightened Rishi-s wrote these texts so there are secrets within secrets. That is why I always say never read Sanskrit books which have been translated into other languages. Or if you read them never believe that the translator has got the correct meaning of what the Rishi actually wrote. Best is to learn Sanskrit yourself.

Now if I write this same sentence in Sanskrit. ‘Aham Manishh asmi’, then here is what you get. ‘I, self-radiant, truth, certainly, surely, indeed, verily am the wisdom, reflection, intelligence, idea, desire, conception, power, master, strength, the Lord of the Mind.’ This is the power of Devbhasha Samskrutam. Now tell me can you ever trust ‘translations’ of Sanskrit texts?

So, if you can, think of our deities names as adjectives. Shankar means happiness. Shiva is the auspicious one. Ganapati means the energy which enters the individual souls and causes change. Nandi is intelligence. Laxmi is the one who has a recognisable sign. Sarasvati means the one who flows. Ganga is the one who moves very fast. Krishna means the unknowable blackness which pulls. Ram is happiness. Dev is radiance. Bhagwan is the one who has all auspicious qualities. Each of these Sanskrit words has several meanings in addition so every deity of Sanatan Dharma is more like a collection of attributes. The deities are not humans, even though we have got used to seeing them as humans. Deities in Hinduism are pure consciousness defined by some attributes. Their names are not proper nouns but are adjectives. Think of them in this way and you will get more insight into their real natures. (I wrote on meaning of the Navavarna mantra post here) 

Now what is Sanatan Dharma/ Hinduism? To understand Dharma you have to understand the Shatdarshan shastra. I have written a post here on these 6 darshan shastra-s. It is not the work of one lifetime, but you carry on whatever you have learnt into your next lives.

Our ‘God’ is the highest conscious intelligence, non-dual, Paramatma, Parabrahma, Paramtattva, Nirvishesh Brahma, Advaita etc. This is the key deity of Sanatan Dharma, the only ‘deity’. You yourself are this Parabrahma. So essentially you worship your Self.

The Ved (Ved, Brahmana, Aranyaka, Upanishad),are the final authority for everything in our Dharma. The crowning glory of the Ved are the Vedanta, which deal with the Advaita in great clarity. The 10 major Upanishads with the Mandukya Upanishad occupy the highest place. The beautiful Mandukya has only 12 lines about the Om and the Paramtattva. 

So now about Om. Om is also not the actual Paramtattva. Om is the nearest thing to it. Something like a ‘Moorti’ of the Advaita. A Moorti that you see in temples is made from stone, metal etc. But here you are required to visualise a Moorti made of conscious energy. Om is a Moorti of the Paramatma. You have to visualise Om with this intention and understanding. This is difficult for beginners on the spiritual path.

The course work has to suit to the student. You cannot teach a 1^st std child, the syllabus of a PhD. Ved and the Vedanta is PhD course work.

In Sanatan Dharma the main texts are the Ved (Ved, Brahmana, Aranyaka, Upanishad), these have the highest validity, they are the source of everything. Then are the Itihas, histories, eg Ramayan, Mahabharat, the actual incidents are given in detail. They also have philosophy ie attaining Moksh and practical stuff like how to manage a kingdom (ever read the original Mahabharat or Ramayan, it is much much more than a simple story). These Itihas conform to the Vedic principles. Then we have the Puran-s. In these additional historical incidents are given, more philosophy, more practical stuff etc. And anything written here has to conform to the Vedic concepts and the broad outline of the Itihas. The 18 Puran-s written by Ved-Vyas are given more prominence in this category. And there are the several commentaries, Bhashya, treatises, practical work, more philosophy etc written on these texts by enlightened Guru-s like Adi Shankaracharya and others. This broadly is the corpus of texts available in Sanatan Dharma. Regular Hindus never read these texts, unfortunately.

All Shastra, all pujas, all yajnyas, all mantras are secretly hidden in the Ved. It is a huge huge repository of knowledge. eg the entire Shri Vidya which deals with the worship of the Devi Lalitatripursundari, the Maha-vidya-s etc is from the Ved. It is one of the many Vidya-s mentioned here. Another Vidya is the Chakshushi, I have written about it briefly in this post. All these Vidya-s will take you to the Parabrahma if used in the correct manner. Jyotish is also a Vidya.

These different texts describe the same Reality in different perspectives in different words which are suited to people of different mindsets. eg If you read the texts on Devi Lalita, it is given that the Devi just looked at her toe-nails and the 10 Vishnu-avatar-s manifested from here, did their work and again got reabsorbed in her. This is obviously different from what we popularly know about the Vishnu-avatar-s. In the Shiv Puran, there is a Shiv Gita which Bhagwan Shiv narrated to Shri Ram at Rameshwar before his war with Ravan. eg Bhagwat Gita, most people believe that this is the only Gita, the highest teaching. But if you open the Ishwar Gita, it is very similar to Bhagwat Gita. If you read the Shiv Gita, this is also similar and also has a Vishwaroop darshan. Then you read the Anu-gita which Krishna taught to Arjun after the war, and this is very different from the Bhagwat Gita which he taught first. There is a vast ocean of philosophy, spiritual practices, teachings, discourses in Sanatan Dharma. If you randomly read from here and there, you will get extremely confused. 

In the past and even now, Dharma is facing a lot of challenges. The Dev-Asur Sangram, ie the constant war between radiant and dull energies is always on at different levels. It is still going on now and will always occur. Sometimes the Dev will have the upper hand and sometimes then Asur might seem to be winning.

There are numerous examples where our temples, libraries, universities and their custodian Brahmins were very viciously destroyed. The horror in Kashmir where specifically Tantra and its genuine practitioners were systematically wiped out over the last 500yrs or so. The oldest physical book of Valmiki Ramayan was burnt when the Britishers burnt the libraries in Kolkata about 200yrs ago. Tipu burnt ancient libraries, manuscripts and their custodian Brahmins in South India about 300yrs ago. More insidious was that the invaders injected nonsense in our books and are still doing it. People who do not follow Sanatan Dharma are writing translations of these texts with the express purpose of altering their meanings.

It is difficult to find authentic texts and more difficult to find a real Guru. Also we have forgotten our mother-tongue Sanskrit, thus are a highly confused directionless lot.

Back to Om. Vedanta clearly states the Om to be the Paramtattva. Focus on the Om and you will gain that realization. The Ved describe Om and how it has manifested the universe from itself. Om is the first vibration, the first movement. The main deities described are the 33 koti devata ie the 8 Vasu, 11 Rudra, 12 Aditya, Prajapati and Indra. They further create the universe and everything else in it. These are the backbone of the creation and they actually exist in our backbones, in the Sushumna nadi. 

You create your own universe. This concept is also rather difficult for beginners to comprehend. I have put posts on using energy consciously, try doing some of these exercises to actually experience how you can create. Once you succeed at an ‘energy experiment’, your perception changes forever. 

Indra as well as all the other Vedic deities are pure energy. They are not human figures. Now for the students who could not comprehend the highly esoteric Ved-s, more human looking deities was introduced in the Puran-s. All the energies were given human forms. Prakruti was given a Moorthi of the beautiful Devi Lalitatripursundari. The tri-Gun, Satva, Raja, Tama were given human forms so we have the Tri-dev etc. All these Puranic deities are also conscious energies, but described in more human terms so that we can relate to them more easily.

But every shloka, every stotra, every sukta in this vast ocean of Sanatan Dharma describes only the Advaita. This might be difficult for beginners to believe but eg. every one of the 1000 names in the Vishnu sahastranama are ultimately dedicated to the Parameshwar, from the first ‘Vishnu’ to the last ‘Sarvapraharanayudh’ all are linked to this Parabrahma. The Dasha-Mahavidyas are the energies of the 10 directions, the intelligence of space, their essential nature is also the Paramtattva (post here). Now open the Devi Atharvasheersha, She says ‘Aham Brahma swaroopini’ in the first line. If you open the Ganapati athavasheersha, it says that Ganapati is the ‘pratekshya tat tvam asi’ in the first line itself. ‘Tat tvam asi’ is a Mahvakya of the Ved. So all deities are essentially Parabrahma.

There is only one thing that is worthy of being known. That is Parabrahma and we do it through his Moorthi, Om. You are Om, I am Om, we worship Om and whatever we do or see is all Om. Eg In all stories/ allegories, you see that the Tri-dev are generally in Dhyan or in deep contemplation. Who are they doing Dhyan of? Who is the essential consciousness within them? In the Puran-s, it is mentioned that the Tri-dev did intense Sadhana to get to this position that they enjoy. Whose sadhana did they do? To become aware as ‘Indra’, 100 ashva-medh yajnyas are necessary, who are they dedicated to? So just think, to become aware as ‘Om’, what level of intensity will be necessary?

In our pantheon of deities and the humungous mass of stories/allegories, if you get into who was whose husband, whose wife, who was the father, who was the son, who came first and who came later, you will get very confused. The Ved say this same thing, the serious aspirant must focus on the ultimate reality, not on anything else. 

You should not think of yourself as Indra or Vishnu or Shankar etc or any of the Vedic or Puranic deities. Think of yourself as Om, the Parabrahma. Try to explore and locate that Supreme consciousness within.

And finally to sum up this discussion.

Do what your Sat-Guru teaches you to do. Practice under the guidance of a Guru. Follow what he tells you. This is why the Sat-Guru in Sanatan Dharma is so essential. Without the blessings of the Guru you cannot do anything and cannot realise anything. 

Eg if your Guru teaches you from the Bhagwat Gita of the Mahabharat. You will think of Shri Krishna as your adored deity. First as a Vishnu-avtar, then as you go deeper into him you will realise that the Gita talks about the Advaita. The real Krishna, who ‘pulls’ you inwards is the Advaita. The ‘unknowable blackness’ is again a negation of this created universe. Your Guru will help you experience this essential attribute of ‘Krishna’. 

Eg if your Guru teaches you to worship Devi Lalitatripursundari. You will worship the Shri Chakra/Meru with mantras. Initially you might think that you are worshipping a beautiful Devi wearing red sari, jewellery, 4 hands etc. You might call her Mother, Maai, Aai, Mataji, Maiiyaa, etc but later you realise that her name Maa is most apt. I have written this post on this word ‘Maa’, it is a negation, essentially means ’No’. Her subtlest nature is a resounding negation of the creation you see around you. She is Advaita. This realisation will come at the highest levels of your sadhana.

Eg if your Guru teaches you Gayatri puja. You might think that you are worshipping a beautiful Devi with 5-faces etc with her Gayatri mantra. But later as the mantra pulls you inwards you realise that the ‘Savitra’ in the Gayatri mantra refers to the internal illumination. Your are worshipping your own Luminous Self. And this is the Advaita.

Eg if the Guru starts off with the pure Vedanta. This is a rare Guru and an equally rare student. You will then go directly to the Upanishad. He will teach you ‘na iti, na iti’, not this not this. Again the negation of the Maya of creation and the single pointed focus on the pure Om. Read about the Om, practice Om, experience Om and thus the Paramtattva whose Moorti Om is.

A Guru teaches what he has achieved, ie he can teach only what he has the ‘adhikar’ to teach. ie, a History teacher will teach History not Math and a 1st std teacher will not teach PhD students. If a Guru has practiced the Gayatri mantra he will guide you with the Gayatri mantra. If he visualises the Gayatri as a Devi in a red sari then he will teach you this same visualisation. If he has visualised the Gayatri as the Advaita then he will be able to guide you till this final destination. When you get blessings of a Sat-guru, the Atma-jnyani Mahapurush, the Jivan-mukt, ie the Parabrahma only then will you attain Moksh.

So choose your Guru very carefully. Guru is a force which pulls you towards your Self. And there are several pretenders who claim to have got enlightenment or claim to converse with the deities etc. Evaluate carefully before accepting someone as your Guru. If you do not have anyone around, try to follow some daily routine (post here on daily pujas). Get your own intention moving, desire to know your own reality. If you desire it, it will happen. When the student is ready the Guru will manifest. 

So Dear Reader, this is a rather rambling answer to your question, see if it helps you in some way.