Hey there, thank you for playing!
So, i think i failed to explain better in the game (close to the end it does explain a little). it was the first game i made, so there are some flaws, hahahaha.
Anyway, each "world" is an elemental temple, earth, wind, water and fire. when you complete each you gain a stone that fill one of your shields socket (the ball XD). when you complete all four you gain access to the dark temple, where you can get the immortality potion ^^