hit by Grendelkin rock

The grendelkin lowered his arm and I saw a quick flash of yellow eyes, a hideous face, and a mouthful of fangs. Those teeth spread into a smile, and I realized that I might as well have hit him with the stream of water from a garden hose, for all the effect the fire had on him. He moved, an abrupt whipping of its massive shoulders, and flung a stone at me.
Take it from me, the grendelkin's talents were wasted on the abduct-rape-devour industry.
He should have been playing professional ball.
By the time I realized the rock was on the way, it had already hit me. There was a popping sound from my left shoulder, and a wave of agony. Something flung me to the ground, driving the breath out of my lungs. My amulet fell from my suddenly unresponsive fingers, and the brilliant light died at once.
Dammit, I had assumed big and hostile meant dumb, and the grendelkin wasn't. It had deliberately waited for Gard to charge forward out of the light of the dropped flare before it threw.
"Wizard!" Gard bellowed.
I couldn't see anything. The brief moment of brilliant illumination had blinded my eyes to the dimmer light of the flare, and Gard couldn't be in much better shape. I got to my feet, trying not to scream at the pain in my shoulder, and staggered back to look down at the room.
The grendelkin bellowed again, and Gard screamed—this time in pain. There was the sound of a heavy blow and Gard, her hands empty, flew across the circle of green flare-light, a dim shadow. She struck the wall beneath me with an ugly, heavy sound.
It was all happening so fast. Hell's bells, but I was playing out of my league, here.
I turned to Mouse and snarled an instruction. My dog stared at me for a second, ears flattened to his skull, and didn't move.
"Go!" I screamed at him. "Go, go, go!"
Mouse spun and shot off back down the way we'd come.
Gard groaned on the floor beneath me, stirring weakly at the edge of the dim circle of light cast by the flare. I couldn't tell how badly she was hurt—but I knew that if I didn't move before the grendelkin finished her, she wasn't going to get any better. I could hear Elizabeth sobbing in despair.
"Get up, Harry," I growled at myself. "Get a move on."
I could barely move my left arm, so I gripped my staff in my right and began negotiating the precarious stone stairway.

Side Jobs, Heorot, Page 139-140