rumbling titan

The Rumbling (地鳴らし Jinarashi?) was a cataclysmic event involving Karl Fritz's Wall Titans marching across the earth, destroying all life upon it. attack on titan chapter 99 It was a key deterrence factor for the Subjects of Ymir on Paradis Island, until the year 854 when Eren Jaeger unhardened the Walls, freed the Wall Titans, and began the Rumbling