What is Transmog

One of the many new features coming to Legion is an improvement made to one of the features most players already love. Transmogification. Transmogging allows players to replace gear items appearance that with the look of a different item. Some players go to great lengths to collect items to add to their collection so that they can always fit a theme or style, mismatch horribly or match from head to toe all the time. Other players enjoy changing their transmog based on many things, perhaps they got a new weapon and they want to complement that with their gear fitting the same color theme, or perhaps change it to be entirely all pink during the love is in the air event. For whatever reason, people really do love transmogging, however ever since the feature was introduced in patch 4.3 Cataclysm the bags and banks of players have become encumbered with...everything...At this point we could probably start a show called "Warcraft: Transmog Hoarders".
However in Legion, they finally understand the need and love that the players have for transmogging, and offer us some new improvements to the system! Adopting bits from the same system in Diablo 3, with a few little touch ups to to make it work even better in Warcraft, this system will be one of the many positive features in Legion to come.
There is a new Wardrobe tab in Collections which opens up your collection of appearances. You can see items for a particular slot at once, filter by different sources, and sort by what you have/what you're missing.