The Founding Titan is the progenitor of all Titans, the first Titan from which all others descended. Its power is absolute control over the Titans and Eldian people, able to command every Pure Titan and shifter connected through the Paths network. Only those with royal blood can unlock its full potential, though non-royal holders can still use limited abilities. The Founding Titan's power has shaped the entire history of Eldia and Marley for nearly two thousand years.
The Founding Titan's appearance and size are not fixed — Ymir Fritz's original Founding Titan was enormous, towering over the landscape when building Eldia's infrastructure. Karl Fritz's Founding Titan had a skeletal, emaciated appearance with rib-like protrusions and a long, thin body. When Eren Yeager fully awakened the Founding Titan's power, its form became a colossal skeletal creature with spinal cord trailing into the Paths dimension. The Titan glows with a bright, pulsating energy when actively using its coordinate powers to command other Titans across great distances.
The Founding Titan can control every Titan in existence, commanding them to attack, stand down, or perform specific tasks through the Paths coordinate network. It can alter the memories of all Eldian people, erasing, modifying, or implanting memories on a massive scale across generations. The Founding Titan can modify the physical biology of all Subjects of Ymir, making them resistant to diseases or changing their body composition entirely. With full royal blood activation, the user can create an army of Colossal-class Titans from hardened, ancient walls. The ultimate power of the Founding Titan is the freedom to reshape the world, which Eren used to initiate the Rumbling and destroy humanity beyond Paradis.
Ymir Fritz was the original Founding Titan, a slave who gained Titan powers two thousand years ago and built Eldia's empire. Karl Fritz took the Founding Titan to Paradis, creating the Walls and erasing the Eldians' memories of the outside world. Frieda Reiss held it briefly before Grisha Yeager took it from her, and he passed it to Eren Yeager. Eren awakened the full power of the Founding Titan by touching Zeke, the royal-blooded Beast Titan, and used it to free Ymir Fritz from her two-thousand-year enslavement in the Paths, ultimately ending the Titan curse forever.