While his attack does manage to hit the dragon, who respond by snapping at him and likely sinking his fangs into Caiphias' leg, neither of them get much of a chance to do more, as the now-weakened floor gives way, and send both of them tumbling down into the common room below, crashing heavily onto a table in the main room, cracking it beneath them. From the bedroom above, there's the hiss of magic, as MEridia finishes her spell, and the oppressive slowing shield around the dragon vanishes, and the light slowly begins to return, to reveal the dragon looking ready to make his retreat.