rumbling (shingeki no kyojin)

It involves the unhardening of all the walls of Paradis Island and the unleashing of all of the Colossal Titans that are buried within them to rampage all across the world, an act that can only be done with the power of the Founding Titan. When Eren Yeager takes on the power of the Founding Titan, he sets this event in motion in a bid to destroy all of humanity outside Paradis.