Mauth is a living magic that lives inside of the Soul Catcher.
Mauth is one of the strongest forms of magic in the series. It gives the user the power to help shepherd ghosts to the other side, as well as many other powers that will assist in doing that. For example; Mauth gives his users the power of windwalking which is the physical magic “of speeding through the trees in the blink of an eye” (A Reaper at the Gates).
Mauth possesses the power to bring escaped ghosts back to The Waiting Place.