Blizzard has released an official Warbands preview detailing how currencies, transmog, achievements and more will work!
The Warband conversion process can take up to 20 minutes or longer, and depending on the amount of data being processed, there could be a login queue.
The new Warbands system is effective for all characters on a player's Battle.net account and the items, Collections, and progression they share. It's important to note that your Warband is limited to characters within a single region (for example, the Americas or Europe) but spans every realm, faction, and even subscription you may have within that region.
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When you log in to the game, you'll see a selection of your characters on the login screen, waiting for you to choose who you will go on your next adventure with.
You can assign four characters to one scene, with more scenes planned for you to collect in the future.
In addition, to make it a little easier to see who's who in your Warband at any given moment, there’s additional information about each character during character selection.
Once in a Warband, you will no longer need to swap between realms to see characters on those realms. The one exception is if you have multiple World of Warcraft subscriptions within one Battle.net account.