He could only become a real wizard after he had grasped the 'Move in a flash.'
Every occupation in the Holy continent knew about this. The main thing that made a wizard different was not their knowledge or their scary spells; it was their ability to move in a flash of light.
This allowed a wizard to retreat or attack at will. Therefore you would be able to see the shadow of wizards even in the most dangerous place.
Another special thing about wizards was their lifespan. Their lifespan would shoot up dramatically once they reached an intermediate level. That was why the dwarfs and humans had accumulated so many intermediate wizards throughout the centuries.
These intermediate wizards were the core power of the dwarfs and humans. Not only in the Holy Continent but the Dark World as well.
Especially fighting inside a cave. The countless turns and corners could dramatically reduce the potential of a wizard if they could not move in a flash.