User blog comment:7-45 Fire/How Fairies came to be./@comment-31892545-20170812030640/@comment-26569404-20170812092234

Acheron didn't create the Legendarium World. He created a portal from it by compiling existing legends into a book (the Legendarium). The name "Legendarium World" was probably given afterwards, since everyone associated that world with the book itself.

The Ancestral Fairies left the Legendarium World on their own using the Mythix Wands. That makes sense, since the Winx didn't need the Legendarium to travel back and forth. So that part isn't contradictory.