C766 Birds Fly but

I could only watch as Ouyang Huo's body flashed at the entrance of the valley and disappeared from my sight. The feeling that he gave me was that the valley was like a pool of thick ink. After Ouyang Huo went in, he was dyed black by the ink.

I really didn't understand why there was such a huge difference between the inside and the outside when they were only a step away from each other