User will have scale like skin.

Pros:
-user will have fangs
-user's blood will be poisonous
-user can make scales tougher
-user will have snake like instincts

Cons:
-user will pray on smaller animals
-user will be harder to treat for disease
-user will shed their skin
-tougher scales fall off after a couple hours
-poison will melt anything it touches

Weakness: a lot of cold
Users will slow when cold, going into hibernation