As with Nav, Vyraj has to be reconstructed from fragmentary evidence rather than read from a surviving native scripture, drawing on Christian-era chronicle references, comparative Slavic linguistics, and above all folk custom that persisted for centuries after formal Christianisation reframed or absorbed the older belief.
Ukrainian, Russian, Polish and other Slavic folk traditions preserve variants of the bird-migration belief well into the modern period, sometimes explicitly Christianised, with Vyraj reinterpreted as a stopping point on the way to or a reflection of the Christian Heaven, showing the same pattern of syncretic layering found across much of post-conversion Slavic folk religion rather than the older belief being cleanly erased.
Modern Rodnovery, the Slavic Native Faith revival movement, has drawn on this reconstructed material in developing contemporary practice, though as with Nav, serious scholarship treats the details of pre-Christian Vyraj belief as inherently uncertain given the absence of any surviving native theological text describing it directly.