Character customization in Aion

Those classes can equip armor as "appearance gear" is a unique game capability in Aion. Specifically, Appearance gear of a type is a limit placed on that player in the case their classes allows. For instance a spirit walker does not allowed to wear plate gear.

Bear in mind, similar appearance slots system has been fitted in EverQuest II since mid-2oo8. A player is prevented to wear appearance gear of a higher mitigation than his/her effective armor in Aion – that is a significant difference. For example, in the event that a player wields cloth armor, the player will not be allowed to wear a chain or leather appearance even with his class permission. However, there is no such limitation in EQ2.
To better understand how the system works, a player can experience it by changing the graphics of most weapons and armors with the same type currently in inventory. There aren't any "appearance slots".