The subject of this article or section is part of WoW's Anniversary, a seasonal event that lasts two weeks. Once the event has run its course, this will no longer be available until next year, but there are no guarantees.
A Slightly More Urgent Letter from the Timewalkers was included in the [Anniversary Gift] that was mailed to all player characters that logged in during [WoW's 13th Anniversary].
As a quest objective
This item began  Interesting Times.