This is Basian Maraz. He's a nurse shark.

And your mind is his dinner.

His bite, while leaving a physical mark, will also take away some part of your mental state. This part of his victims stays with him always, and he can recall it whenever he likes. Memories, motor skills, sanity...he keeps them for himself, and can use them against his victims as well.

So...if he takes your ability to move, for instance, you'll only be able to do it when he lets you. Have a memory that's dear to you? It's his now, and you can only have it back when you do what he desires. Enjoy thinking rationally? Well that's just too bad. The only rational thoughts you get to have are the ones he lets you have, and he's likely to mess them up so that they're only 'rational' in a way that pleases him.

How does he do this?

What he steals from you, he keeps in a tooth. He'll then pull it out of his mouth (as a shark, he'll just grow a new one back shortly) and make a piece of jewelry out of it. Using this, he can manipulate whatever asset he stole from you by simply wearing the piece. He may sell it back to you...but you'll have to wear the tooth or keep it on you in some way if you want to have that stolen asset back. So if you lose the tooth, or it breaks...

...no more of that for you, I'm afraid.

I have no clue what I'm using him for quite yet, as I have no place in my plots where I feel he's needed...buuuut...

I like him, and I'll figure it out.