Which Might and Magic universe are you referring to?

I completely forgot that the fifth installment was developed by a Russian team. So, the Russian names for the factions are quite authentic – and these are not translations, but original names. How they translated them into English is a completely different matter.
And in general, the principle itself has changed – in Enroth, identification with a faction was based on the type of castle, while in Ashan, the races are identified as races, not as appendages of castles.

As strange as it may seem, the game was still developed in English. At least the English editor suggests this (there was no Russian version at all). In addition, the entire world, all the original names, were created by Ubisoft. It is possible that they initially developed Ashan in English as well, as the most universal language.

But I also don't think that the faction of light elves in the Russian localization should be called Sylvan. And the Russian meaning of "Inferno" can generally be associated with demons, as they are not known for their culture.

Regarding the connection to Ashan... Why can't these worlds exist in parallel? Ashan was created by Ash, the rest of the universe was created by someone else, and then they intersected...