"Lumos!"

With the light of her wand leading the way, Sierra walked (yes, walked, as the tunnels had conveniently gotten higher by now) through the tunnels. She had to be nearing the end. Sure, the castle was humongous, but she'd been at this for nearly an hour. Surely the professor didn't hate them that much so as to make this course go on forever!

Up ahead was a wall, so Sierra raised her wand toward it as she kept walking closer and closer. With a downward slash, she said, "Diffindo!" Ha. She was getting good at this! ...or not. She hadn't even taken a single step forward when she saw another wall just behind the first one. She glared at it then severed it, as well. This went on until she'd severed through at least five walls. She should be good, great even, at this charm by now.

Why were there so many blasted walls back to back, though?! She severed through a sixth one, a seventh one, and then... Oh, wait. Could it be?! Up ahead, she saw a little hole with light shining right through it. There was light up ahead! Just up ahead! Sierra ran forward and approached the hole. Downward slash..."Diffindo!"

The wall broke into two parts, and then she stepped through, fully expecting more tunnels up ahead. Instead, she was more than happy (for once in her life) to see the classroom. She'd reached the end! Thank Merlin!!! She stepped forward and collapsed into a nearby chair.