Psychics, Assemble!

[Urban High Martial Arts] [Supernatural Powers] After walking about three miles, the fog began to change color. The pure white turned into a grayish white, like the color of old newspaper left out too long. The light dimmed, and the canopy overhead grew denser than before. But all the thicker branches were dead, without a single leaf, like a gray wire mesh stretched across the sky.

Shen Wangshan stopped for a moment. He raised a hand and signaled for the flock of pigeons to descend thirty feet. They circled twice in the gray-white fog, then climbed back to their original altitude. His expression seemed troubled...

The pigeons said something was blocking the way ahead. It wasn't alive, and it wasn't dead. It was something... that didn't belong on this mountain. Shen Wangshan reached into his hidden pocket, took out the gray-white homing pigeon, and held it in his palm. The pigeon hunched its neck and crouched, wings tucked tight against its sides, feathers trembling slightly. The bird was caught in a tense stalemate, unwilling to fly away but afraid to land.

What did he mean, something that didn't belong on this mountain?