Warbands are on the way to World of Warcraft®: The War Within™! In order to prepare all characters for the transition to the new system, which will occur during the pre-expansion content update, we will temporarily be disabling character restoration. 
For those who would like to restore a previously deleted character, it is advised that you do so before the pre-expansion content update goes live. After the pre-expansion content update goes live, restoration of characters on your World of Warcraft account will be unavailable for a few weeks.
To restore a deleted character, log into World of Warcraft and click the Restore Character button on your character selection screen. Learn more from our support article. Please be aware that any characters newly deleted during the pre-expansion content period will be unable to be restored during this period.

What are Warbands?

The new Warbands system being introduced in The War Within will encompass all of the characters on a player’s Battle.net account as well as the items, collections, and progression they share.
Many aspects of World of Warcraft have been shared across accounts for some time—essentially a Warband. This includes collection of pets, mounts, transmogs, heirlooms, and more. With the release of Warbands, we are significantly expanding what additional aspects of the game have Warband integration. To name just a few changes:

New reputations and Renown tracks will be Warband-wide.
A new Warband bank will allow you to easily store and share items between your characters.
The ability to collect most item appearances with any character in your Warband, regardless of their ability to equip the gear.

Learn more about Warbands in our previously published overview.