@Sviatogor We know little about Slavic mythology. All we have is reconstruction. That other story is also slavic mythology heritage. That story goes on and on. Eventhough our ancestors accepted christianity their old traditions are strongly incorporated in christian believes. Oral history is one the greatest sources for our old religion.
In that picture you posted in the right bottom it is said smok. It is often used in northern parts of croatia to name a dragon 😉