[Wrana]

To Kuritza:

Thats because bylinas are centered aroud several heroes who lived at about the same time Ilya Muromets, Dobrynya Nikitych and Alesha Popovitch, mostly. But druzhinas arent necessarily assotiated with that particular Knyaz, or any bogatyr at all.

Well, you are just wrong: Ilya Murometz (probably Murmanin, or Morovlenin - such versions were also used) may be a combination figure (he is also noted in German tale originating at about 11th century; some Jew enthusiasts even say that he was a Jew & his surname is actually Morovlenin, meaning "wall-builder" ), but if bylinas' hero is based on actual man - than he is most probably Ilya 'Chobotok' ("The Boot" - for fighting the steppe invaders with such a weapon!)) Pechersky, living at 12th century, buried at Kiev monks' ossiary and later declared a saint by an Orthodox Church;
Dobrynya Nikitich is most probably based on Vladimir's uncle - however, there are 7 warriors of the same name in annals...;
Alexander 'Alesha' Popovitch, afair, also lived at 12th century & became famous for declaring that it's wrong for Russian warriors to fight each other serving local knyaz & far better for all to fight common enemies serving Veliky Knyaz of Kiev (who was at the time formally considered a head of state - though most times he didn't even bother to try to order local knyaz...);
Bogatyr Zhydovin ("The Jew") is probably based on Khazar Kaganate's warriors - & so his prototypes may be placed at 9th-10th century - or else this figure appeared in bylinas much later, probably in 15th-17th century;
Volga / Volkh Vseslavich - the only one of bylinas' figure who can be considered a "mage" - may be based on Knyaz Oleg (Helgi) Veschij ("The Wise") - who was regent before Vladimir's father;
et cetera, ad nauseam - there are, as I've heard, even bylinas about Ermak Timofeevich - a completely historical figure who conquered Siberia at 16th century... So bylinas, as is the case with other legends, place together heroes and situations from different times and places & often use combination figures/situations.

...By the way. Knyaz "Vladimir Krasno Solnyshko" from these Bylinas is actually Vladimir I, around 960-1050, who baptized Russia.

By the way, would you be so kind as to give me title or link to any SCIENTIFIC work which states so. I've certainly seen it enough in popular books which so love simplify everything..

Not much is known about Russian paganism, thats true. Christian clergy did its best to wipe all traces of pagan traditions, and they succeeded.

Please, spare me Neopaganistic slogans. There are much simpler reasons: the Slavic people, unfortunately, had no written culture until appearance of Christian missionaries - and those were simply not interested in writing down things they considered to be just a bastardization of Hellenic paganism (while pagans did not want to learn anything from Greek monks). The truly common written culture formed in Novgorod only well after Christianization. While Ancient Greeks, as well as Scandinavians, had written culture during their heroic age, and Arabs hail from the region where written culture was relatively common even before their advent... See, no need to make "Public Enemies #1" of Christians and form a historical OGPU to fight them...
As for Simargl - I have noted this earlier, while the version of one figure becoming many, while popular afaik among modern occultists, and probably true in cases of Indian mythology, was not proved to actually occur in mythology of other peoples. I even suspect that true situation was often the other way around...

And why, I ask of thee, did Vans 'conquer' Bogarus? Logically, they were invited to rule!

Well, firstly, I've seen it before in some flavor text here...
Also about Rurik - he was certainly invited to try to make order in Novgorod melting-pot... from Staray Ladoga, which, for those who didn't know, is also deep inside Slavic lands (or Finnish - as population here was mixed). While appearance of above-mentioned Oleg in Kiev, as you'd already noted, certainly had all properties of military conquest...
To All on Vyedmas, etc.:
I think that etymology from a word meaning "to know" is actually quite common - even in English, "wizard" has common root with "wise". While "magic" is derived from title of Zoroastrian priests and wise-men... However, Finns were actually considered to be mighty sorcerers - certainly by their Scandinavian neighbors, & probably by medieval Rus as well - at least in Pushkin's fantasy poem "Ruslan and Ludmila" which was written in 19th century, sorcerer characters are either Finns, or of Arabo-Persian origin... And also actual traditions in this respect could be very close for Finns and East Slavs - especially as they lived close to each other for some hundreds of years.