Invocation

An exchange occurs between that which is invoking and that which is being invoked.
Invoking is a mutual interaction. A pulse of sound/light upon encountering an obstacle will be trapped bouncing back and forth between it's origin and the block. With each bounce, a residue is left behind. Eventually it may gather enough "weight" to cause a movement. The pulse begins to assume the shape allotted within the dark matter. The dark matter is slowly transformed by the pulse.