The idea of paths came from noticing that the Nine Titans are sent to a random baby among the Subjects of Ymir, regardless of distance or blood relations, if they die without being eaten. This implies that the Subjects of Ymir are all connected by something invisible, and what connects them are called paths.
Paths serve as channels for the transportation of several things, such as, but not limited to, memories and thoughts from other Subjects of Ymir, and the flesh and bones that make up a Titan's body.
When paths cross, the point is known as a "coordinate" (座標 Zahyō?). The Founding Titan is the Coordinate where the paths of all Subjects of Ymir and Titans cross. It can alter the memories of Subjects of Ymir, and command all other Titans. However, royal blood is required to access the power; if one is not a royal, it can still be triggered by touching someone, preferably a Titan, who has royal blood.
Although paths are invisible in the physical world, they can be seen by entering an unknown land. There, light-colored soil covers the ground and paths manifest as trails of light in the sky, similar in appearance to an aurora. Ymir entered that land after she gained the power of the Titans.
During the year 845, after Ymir devoured Marcel and gained the power of the Titans, she awoke in the unknown land. When she saw the paths in the sky, she called them "freedom" spread out before her. She vowed to live a life without regrets afterward.