This item is a quest reward from [100 - 110] In the Blink of an Eye. It functions as a secondary Hearthstone for the Dalaran, leaving players the ability to bind their primary hearth wherever they please.
If you have lost your Dalaran Hearthstone, you can talk with Amisi Azuregaze at the Legerdemain Lounge of Dalaran to replace it.
Since patch 7.0.3, it was possible to obtain this item simply by talking to Amisi in the Northrend Dalaran. This was probably due to a failure to differentiate the Amisi from her version of the Dalaran located in the Broken Isles. It was corrected afterwards in an undocumented hotfix.