Complete story — includes the ending
Squad Levi storms the cavern and forces Kenny's squad to retreat. Rod explains that the three Walls were built a century ago by their ancestor, the First King, who used the Founding Titan's power to erase the memories of all citizens (apart from the immune bloodlines) so that no one retained memory of the world's history beyond the Titans' arrival one hundred years ago. Generations later, Frieda inherited the Founding Titan, along with the memories of their world before Titans. Rod wants Historia to inject herself and become a Titan to eat Eren and reclaim the Founding Titan within him that he gained from eating his father, as only the Reisses can wield that Titan's power. Historia realizes that Rod's true intent is simply restoring his family's power; the Reisses cannot save humanity due to the First King brainwashing everyone. She breaks the syringe. Desperate, Rod laps up the serum and transforms into a massive Titan.
Sources and content license
Source and revision history · Adapted from Wikipedia contributors, Attack on Titan season 3. Reference markers and HTML formatting removed. · Content license