You can trigger the mini-playfield from the Oasis, or the Palace. Hit the Oasis from the upper right bumper to the left, hit the palace from the upper left bumper to the top right, but you must have the right flipper lifted to hit the palace, or the ball won't get through.
The Oasis always triggers the game, the palace will only do this if the book of tales is not lit, otherwise you may go to the magic carpet or escape mini games, depending on how many orbits you've hit. I found the palace much easier to hit, once I knew what the trick to hitting it was. I suggest hitting this achievement early in your game, as you can unlock the carpet and magnet games as you play, and then the palace will sometimes trigger those instead, even when the book is not open.
In the game, you have to clear all of the scrolling guardians, and there seem to be about 3 screens worth, you don't need to then successfully exit, but you do need to clear the last 2 at the top, the achievement will unlock when the last guardian is cleared, before you exit the playfield. If it has not triggered, then you have an off screen guardian that you haven't cleared.
Took me a while, but satisfying when you finally do it!