Since Changes isn't covered by the game system yet I've used the spoiler tag - I probably don't need to but why not?
I think we could model Binder as someone who made a lot of deals on the otherside and could conjure bodies.
From YS274
""...creating enough faux frogs to overrun a city park could be 11 or more—5 for the basic frog, +2 several times over for quantity."
Bump up from frog to the "can't really pass for human" bodies that Binder used would be something like +3 - 5, bring it from 11 to 14 - 16 for a mob of human like bodies.
The deal he made with the otherside thing could be a massive binding that made him famous (say a 30+ step rite that has them at his beck and call for years) or it might be a: "You can't walk around on Earth because you don't have bodies. I can make you bodies. Let's talk." type deal.
Mechanically he would have Ritual (Binder's Path), with Binder's Path being something worked out between the player and the GM to allow him to get his minions from the Nevernever. That or thaumaturgy with lots of refinements in one area... No, he's referred to a one trick pony so that's unlikely that he has the generalist power of thaumaturgy.
What sort of powers would Binder's path have? My view:
- limited conjuration; he can conjure bodies for things but he can't conjure objects
- summoning and binding only for certain classes of creatures
- maybe the ability to enter the Nevernever to bargain, maybe not.
If he has rituals, I see him having focus items to boost his power.
Richard