From the Slavic History
In the legends of many European tribes, including the Slavs, there is the mentioning of Arius who was their ancestor. Most likely it was one of the Atlanteans who begot the northern branch of the modern human race with light skin, which is more sensitive to the ultra-violet radiation scarce at high latitudes. On these grounds, the modern researchers call all light-skinned people Aryans [16,41,86].
Later on one part of Aryans migrated from Europe to America, while another one — moved south-east, to the territory of modern India, Pakistan, Bangladesh, Afghanistan, Iran, and other countries, where they mixed with the aboriginal black-skinned people that lived closer to the equator.
The Slavs represent the Eastern branch of the Aryans. Their history is presented in The Book of Veles  in particular.
The ancient Slavs had an advanced religious culture. They knew about the Creator Who lives in His Abode (they called Him Rod) and about His Fiery Creative Manifestation — Svarog.
And Holy Spirits were called by the Slavs by the name Svarozhichi (meaning children of Svarog).
People also worshipped other individual Manifestations of God, which was based, apparently, on specific knowledge of Them.
There was also worship of particular Svarozhichi based on concrete knowledge about them.
For example, they worshipped Lada — the Goddess of Love (hence the Russian noun lad — which means harmony, and the verb ladit’ — to get on well (with someone)).
They also worshipped Perun — God of military valor and courage.
Invoking Lada and attuning to Her one could learn to love tenderly, “from the heart”. Then they could achieve harmony in their families and become more perfect in Love.
By getting attuned to Perun, identifying oneself with Him, filling one’s body with His Might and Courage one could develop the power aspect of the consciousness and be more successful in repulsing the attacks of enemies.
It is these two qualities that the Slavs respected in people: 1) love, and 2) military valor.
The meditative attunement to Lada or Perun, asking Them for assistance in good deeds, helped people to become more perfect.
And Surya — a female individual Manifestation of the Creator, similar to the gentle light of the morning sun was suggesting Herself as a model for attunement to spiritual seekers who reached a significant level of perfection. Today, Her task is the same — to help people to cognize Svarog and realize complete Mergence with Him.
… All religious people can be classified into several groups depending on the object of their sincere (!) religious aspiration:
1. Those who seek the Creator.
2. Those oriented towards certain Divine Teachers — Individual Manifestations of the Creator.
3. Those who perceive nature as the Living Force — in this case there emerges mythological ideas of specific manifestations of this Force as “gods” of wind, rain, water, the sun, the moon, stones, lakes, etc., as well as of multitude of spirits who surround us, which is the case in reality. This form of religion pertains to people who live in harmony with wildlife and who have never heard about knowledge of a higher level.
4. Those who worship fictitious “gods” — fairy-tale personages or incarnate people who have not attained Divinity yet.
5. Those who worship spirits (including their own deceased relatives).
6. Those who worship non-embodied evil beings for the sake of deriving personal benefit (usually for domination over other people).
All listed categories are always represented in each society. The factor that determines to which group an individual belongs, is first of all the age of the soul, but it also depends on one’s upbringing and free will. Lifestyle also has a certain influence, as well as the environment. I.Zabelin  made a good observation that nomads and hunters “chase nature”, whereas settled farmers live by caring for it. Farmers study nature; they start an “intelligent conversation” with it, giving it grain and expecting a harvest, for instance.
People who made up Slavic tribes also were not of the same soul age, of course. The most evolutionarily advanced of them were members of esoteric schools headed by Divine Teachers. Adepts of such schools were called volkhvy (magus).
In other words, we can see that the Slavic religion was not primitive paganism at all, but rather a quite mature system, which possessed knowledge about the Creator and about concrete Divine Teachers, and about methods of spiritual work in esoteric schools.
Moreover, at that time the Slavs did not know of alcohol; as a “holiday” drink they used so-called “surya” — a “sunny” beverage, made of clabber, infused with herbs, with honey added. It was the Greeks who taught them to drink alcohol later.
Another distinctive feature of the Slavs’ lifestyle of that time was that the human body was not considered “shameful” (which later was introduced by Judaic-Greek pseudo-Christianity). This is evidenced by the fact that all men and women would take a bath together at the same time. “Christians” had not been able to extirpate this custom until the epoch of Peter the Great .
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The Slavs first came to Eastern Europe as a single tribe. But this tribe grew and divided into separate clans, some of which migrated to new territories and settled there.
Southern coast of the Baltic Sea got populated by Russian Varangians, who engaged in sea fishery and trade.
Other clans settled in Southern prairies and became nomadic cattle-breeders (the Scythians and others).
Therefore, we can see that because of the vast territory of settling apart, cultural and religious homogeneity is hardly to be expected among the Slavs after the passing of many centuries.