Yeah, we could use the gathering power trope. He wouldn't be at full strength, but he's at just enough to still be very threatening as he is, so he needs some sort of contact to control beings. It could even be some sort of item in his possession that allows it, like a book or some other item.

Sounds fair. So you want this to start with Botan's explanation? Maybe they're leaving a funeral that Kurama attended out of respect for a classmate?