She didn’t even register the soft hissing coming from the left. She thought it was an echo of their footsteps at first; only when the hissing go louder did she discern it as an outsider sound. Another millisecond of doubt and the snake’s fangs would’ve pierced her shoulder, but somehow Hermione managed to turn her full body to where the snake was, take a step back, and whish the sword where the snakes head was just a moment ago. Her wand illuminated the enormous body of the snake, its wild eyes and mouth full open, hissing out poison, ready to attack again.