So, new OC. This guy's name is Narfi and he is a mirage.
Mirages are a subspecies of parasitic demons, which are mostly invisible. They are invisible to all people, and can only be seen in reflections.
The exception is demons and other hellish creatures that can see mirages on a permanent basis.
Why are these demons parasites? It's simple, they don't kill their victims right away, but prefer to stalk their victims for some time, drinking their blood and spinal fluid little by little.
When the victim collapses from exhaustion, Mirage finishes it off, changing form to a more monstrous one.
Here's a little bit about the details of his Monster form. About the tongue, mouth and wings.