Throughout Mega Quest, you earn medallions by completing each level. Some levels have second and third stages, and will require much skill to complete. There are a total of 67 medallions to attain. Collect them all, and the achievement will unlock. You'll need to collect all medallions in the following chapters:
Chapter 1- 20 medallions
Chapter 2- 23 medallions
Chapter 3- 24 medallions
At first, some levels might seem like they are impossible to complete. The more you attempt them, the more you will become familiar with the level layout because it is the exact same every time. Just keep practicing to try and find the best path the complete it and you will end up either getting lucky or find out a route that is just fast enough to complete the stage.