Mages in this game were graded in two stages: first was through the highest tier of magic they can create themselves.
It was not about casting magic, but creating a spell from scratch.
The highest tier they can create before the right individuals affiliated with mages' association, was their official mage rank graded with the same tier of spells they can cast.
The other stage was the consecutive casting of spells of either a lower tier, or casting of spells that are of higher level than their earned ranks.
A normal mage affiliated with magic tower has to be at least of (tier-2), as in they are at least able to create their own magic of (tier-2) if they wanted an official mage rank.
It was a complicated process, so not many of the players go after it since just being recognised by the system was pretty much enough for them.
