That's a stagger, but the timing of that shout and the way Vanitas seems to be fighting with the collapse that eventually crumples him is too conveniently close to the prickle of magic in the air. Despite how Vanitas meant to hurt, he falls towards Riku.

It says something that Riku's instinct is to catch him before he hits the same floor Riku's been trying to launch him into. That he hefts him up, for a moment peering into his face with his mouth a troubled flat line.

He knows all kinds of magic, not nearly as many spells as Elden might. There's magic that can induce sleep, that can turn the blood toxic, there's even the old, old magic, the kind that can hit pause on time itself.

Could be any of those things, but Vanitas had tried to shake his head like that, and Riku's so strongly reminded of his own echoed gestures and their causes - no, their one cause - that he feels his skin go hot and cold at once.

It's all grit teeth when Elden steps in, angry; it'd be more controlled if he wasn't exhausted in every level, if he didn't have the instinct to fight still boiling in his veins - that adrenaline crash will be something, all right - but instead a hand bolts out to try to grab at Elden by a fistful of his shirt to yank him close.

"What did you do?" Like he isn't breaking anything up, like he isn't doing the right thing, just reacting to the method, "What was that?!"