To my knowledge one does not have to be evil to release the Nahual. I've heard, evil man = evil nahual, kind man = kind nahual. As i understand it we all have a nahual in us, though few ever witness it to any length of time. Witnessing it, and certainly a direct encounter with it can actually kill a person if they do not have a certain degree of power (meaning in this case that they can control their fear).
The bright glowing amber eyes certainly sounds like a nahual. Do the eyes of a skinwalker glow like this?
Flesh and blood, when you think about it, are made up of molecules and even smaller atoms and the particles they are made of (nucleus, electrons, protons). There are vast amounts of space between these tiny particles. That means that we are mainly empty space. Yet something maintains the integrity of our field (holds it all together), into what we call objects. Shamen/sorcerers seem to know the science or at least the rituals of how to disperse, re-form and transport those atoms , across time and across space.