Where Life is vital and evolving and Matter deals with innate properties, Motion is just what it says on the tin. It is the element of change, of movement alone. When used alone on the Fate axis, it allows for items to be imbued with a purpose: it allows for Stuff to be greater than the sum of its parts. If Matter is added, people can be torn apart, their lifeless bodies given new purpose or the very events of the world can be rewritten. Alone with Numbers, it can change one property of an object into another. On the Erf axis, it moves in broad strokes, making items work themselves, moving a unit from one Side to another, even moving time itself via Turn order.
Motion may refer to change, with the impact that:
Thinkamancy changes unit loyalty and knowledge,
Retconjuration changes the rules themselves.