Kicking off the hot mess this is, that's where.

"I've been busy, that's where!" Childermass calls back from where he is, though he does wave, gesturing for Zangetsu to get the hell over where he is. It's stable, for now, and he can't magically jump over to where he is without a usefully placed shadow nearby. "I need your help with something!"

He's sure he owes him a real explanation sooner than later. He'll probably offer one at some point. For now, there's a faerie realm changing shape around them and that takes precedence.