The Ringmaster has a fondness for contracts and stealing mortals.

[ Also "there's lots of magic" is valid, very, very valid. There's the fact that he himself used one of the faerie roads to access the carnival in the first place, too, but that's only one way out of possibly hundreds of showing up here. He won't mention it. ]

And transforming them, it would seem. So, yes, that would be what I believe.