Golden Axe

For this achievement you need to cast level 4 magic with the Barbarian character, otherwise known as Ax Battler.

You cast magic spells by pressing the "Y" button. Magic spells require you to have collected the small blue vases, collect these by attacking the small blue imps when you see them. As you collect these you magic meter (which is located at the top of your screen) will fill up and once you've reached the 4th level you can cast the ultimate spell for this character and unlock the achievement.

An example of his highest level magic spell can be seen in the video below.

* ^{Credit to scir91 for the video}