The Elemental Unrest (also called just the "Elemental Invasion") is a world event that heralds the Cataclysm. Every few hours, elementals attack Stormwind, Orgrimmar, Ironforge, and Thunder Bluff. If players can defeat these elementals and free trapped citizens within their entire city, they will be granted access to two special boss encounters. During the event, a player can venture out into the world to destroy rifts, which grant an achievement only obtainable during the elemental invasion: Tripping the Rifts.