When Sting entered the forest, as he drew deeper, he'd begin to hear whispers. They were nearly inaudible and indistinct, but they were certainly coming from somewhere. The light of the trees became hazy and dappled, eventually fading away to darkness, wherein which the normal looking trees became darkened.
But, this was not the case for all of the trees. In fact, if Sting went farther in, he would find that some trees were... Glowing. They were still green, but they bore a radiance that seemed like filamentation. He'd notice that the glowing trees lit a specific path where the darkened trees did not. This path led deeper into the forest, but also kept the path alight so that Sting would not get lost.