The changeling business is the Fae equivalent of child trafficking. In the old days, they'd do this to punish those indebted to or wronged the Courts. Nowadays, the Courts use changelings to freshen up the genetic pool, as well as provide a variety of servants to their masters. The changelings, having grown up in the mortal world, will serve as contacts and spies.
witches who live in prague live in a wonderland - barely touched by the modern world. cobble stone streets and an ancient culture, their magic comes from dusty books found in empty libraries. prague witches are not to be messed with, there’s something in their eyes, something old, something full of knowledge, something dangerous.