In Slavic mythology, much like in Norse and Baltic mythologies, the world was represented by a sacred tree, usually an oak, whose branches and trunk represented the living world of heavens and mortals, whilst its roots represented the underworld, i.e. the realm of the dead.
While the exact pantheon characterization differed between the various Slavic tribes, Perun is generally believed to have been considered as the supreme god by the majority, or perhaps by nearly all Slavs, at least towards the end of Slavic paganism.