Blessing of Auchindoun

From WoWWiki

If a faction captures and controls the five Spirit Towers in the Bone Wastes of Terokkar Forest, every player in that zone of that faction will be buffed with the Blessing of Auchindoun. In addition to the experience and damage boost, it allows buffed players to obtain Spirit Shards from the all of the bosses in the Auchindoun instances.

Once initiated after the last tower is captured, there is a six hour cooldown before the towers can be recaptured.