Spoilers:
[spoiler]A mysterious metaphysical force that connects all the Subjects of Ymir, allowing for the various powers that they possess. Subjects who were able to glimpse this power described it as "paths" (道). In its fully manifested form, it is visualized as an endless empty expanse of sand with a large tree-like beam of light that branches out.[/spoiler]
paths (shingeki no kyojin)