You skid to a stop at the brink of the cliff, loose dirt underfoot. Breathless, staring straight down at the canyon floor hundreds of feet below, you feel the wind hit your face as it whips upward. Crunching footsteps approach from behind, far too quickly, much too close. You spin toward the oncoming threat, fingers flexing their sweaty grip on the knife in your hand. Too late. A foot slams against your chest, and the ground…