Somewhere far off in the universe, two worlds coesxisted together on the same planet, one was the upper-world (or suface,Terralena) where normal humans and creatures lived, and this world was on the suface of the planet. And the other world was the
under-world (or Niryaka), it was where creatures beyond the ordinary lived, it was also a magestical world where harmony and peace reigned.
These two worlds were close and also far away from each other, you ask me why? They are in the same planet, so maybe it's about the distance but you said they were close? Quite confusing, right? Well, now imagine a normal person from the upper-world, he dreams about meeting mystical creatures and one day "accidentally" he hears about the underworld, he knows that the under-world is under where he lives, the surface, so now he'll try to dig up the ground untill he gets there, he digs up and digs and never give up, he might get to the other side of that world (the upper one) but never get the uderworld, nor find it of course. That's simply because there is a barier, a magical one that protects and divides the two worlds from each other.
And of course there is always a "but".
Somewhere where ground touches the sky, where strange flowers that didn't belong there, grow and form a spiral, and strangely round rocks surround them, that's where the portal to the under-world lives sleeping and waking only when golden color fall off filling the space. But remember that's only from Terralena to Niryaka.