tackles nightmare

Running water. The answer was all around me.
I moved forward, toward the Nightmare. It swung at me with one flailing arm, and I felt it clip my shoulder as it swept down. Then I threw myself into the Nightmare's body, hit it hard. We tumbled together down the slope, toward the newly forming stream.
You ever hear the Legend of Sleepy Hollow? Remember the part with poor old Ichabod riding like blazes for the covered bridge and safety? Running water grounds magical energies. Creatures of the Nevernever, spirit bodies, cannot cross it without losing all the energy required to keep those bodies here. That was the answer.
I rolled down the slope with the Nightmare, and felt its hands tearing at me. We went down into the stream together, as one of its hands clenched my throat and shut off my breath.
And then it began to scream. It jerked and twisted atop me in eight or nine inches of running water, shrieking. The thing's body just started melting away, like sugar in water, starting at its feet and moving up. I watched it, watched myself dissolve with a morbid kind of fascination. It writhed, it bucked, it thrashed.


Grave Peril Chapter 21, Page 209-210