The Transmog Feature gives players the ability to modify the appearance of their Hero and weapons without compromising any of their power.
The Transmog Menu can be accessed via talking to the Blacksmith in the Tavern or in the Escape menu under with the "Transmog" Button or the in the Inventory while being in the Tavern.
To create a Transmog you have to select the small cog at the top on the Banner marked in the Picture many players miss this and get confused now you can create your Hero costume.
The Customization offers a way to recolor, change and hide your Heroes Clothes, Wings, Weapon/s, Accessories and Pet.
If the Hero has an item Transmogged but no actual item equipped it won't be displayed on the Hero despite it being customized in the Costume which makes sense but also might some player believe something is bugged when its actually intended.