As he reaches the cellar door, it bursts open, the white flying, furiously, to get away, defensive enchantments back up to full strength, now away from Meridia's spell. Caiphias can also feel a surge of winds surrounding the dragon, likely protecting it from his wind-based attempts to knock it from the sky. The good news, though, is that it looks like all of those efforts, plus its injuries, are leaving it tired.