NF4

"There are a lot of good things about aura. The defence, improved healing – even more strength. But that doesn't mean it comes without problems. What do you know about aura, specifically?"

"It's the manifestation of the soul. That's all I know other than what it does for people – for Hunters."

"It's enough in this case. Keep in mind that not many people know much about aura at all, the soul isn't something that is easy to measure or experiment on, so a lot of this is guesswork. Simply put, when we unlock a person's aura we enable their soul to manifest as energy outside their body. The analogy isn't exact, but you might imagine a normal soul as being a jar locked deep inside the body, while an opened soul can travel and expel all the way to the skin – it infuses the entire body and protects it."

Nicholas sighed, rubbing one hand against his face, "The problem is that the Grimm hunt humanity through our emotions, and what they lack is a soul. When we unlock your aura, all of a sudden your soul is not just locked away inside you, but sometimes even visible on your skin.