Founding Tyrant
Karl Fritz, the king who built the walls, chose to trap Eldians inside and erase their memories rather than continue the cycle of war.
Vow of Peace
His vow renounces war and ties the Founding Titan's full power to a refusal to fight, creating a false peace built on lies.
Legacy
His decision forces later generations to either accept ignorance or confront a history that could destroy their sense of identity.