From "The Knowledge of Good" by C.A. Kendrick

Jav is an immortal mentoring newly-changed Simon on how they can sense the emotions, thoughts, and will of humans...

"When you were transformed a gray veil fell over your senses. When the power of immortality cleansed you of your mortal frailties, you started to experience the world through senses designed for another place. A place – or dimension – unmarred by evil. Because you are now tuned to this new dimension, you sense this earthly reality in a different way than before. You can feel the evil permeating everything."

Simon leaned toward Jav, riveted with excitement by what he was learning. "Yes," he said, almost breathless. "Exactly. This place and everything in it. It's not like before. Food, colors, smells, sounds; they are all muted by something. I hate it."

"Except," said Jav, "for the inner life of the humans. Even before your transformation I bet you never experienced colors so vivid, smells so intense, sounds so all encompassing as when you are drawing in the flow of a mortal. But all is not beauty and light. Before I even taught you how to examine a flow, I taught you how to buffer. Humans have absorbed the evil around them. But they alone in this cursed world have control over how much of the evil permeates them. They have choice."