Sooth is the Old English cognate of the Norse seiðr. It is spellcraft, the act of manifesting something in material reality through intentionality. In its broadest sense, every act of free will is sooth: the bringing of Heaven into Hell, of idea into matter, of intention into the world.
In Tianmu, sooth is distinguished by the realm from which it is wielded. Heaven-sooth and Hell-sooth each carry a blind spot, the unconscious limitation inherent in operating from one extreme. When consciousness acts from pure purpose, it is blind to desire; when it acts from pure craving, it is blind to clarity. In either case, the opposite force works unseen: pleasure creates pain, and pain creates pleasure, through the simple way opposites interact.
Midland-sooth lacks this blind spot. Because the middle realm is the meeting of both forces in full awareness, sooth wielded from Midland operates with a clarity that neither extreme can match. This is the practical basis for Tianmu's emphasis on cultivating middle-realm awareness.
The most important form of sooth in Tianmu is Ghostsooth, deity yoga, the practice of channelling and becoming a Ghost or force. The methods and forms through which sooth is practised are collectively called Weaving.