Riku is already starting to sprint after Vanitas, one fist raised as if he intends on pressing the advantage won by knocking him back--

A voice shouts ENOUGH and that's not what makes him stagger to a halt so much as the prickle of magic making his skin pebble, so much as the whisper in his heart telling him this has stopped being a fair fight.

His fist drops. Whether Vanitas takes advantage of the opportunity or not is up to him, but for the moment, Riku is calling a truce with the sag of his shoulders, the shocked stare in Elden's direction.