Zhang Xiao was in no hurry to go inside. He stayed where he was, watching with interest.
A sixth-year Ravenclaw student came up the Marble Staircase. Seeing so many people, he paused, apparently wondering why they weren't going in.
Then he carefully studied the Stone Dragon and the inscription beneath him.
"Do Not Disturb the Sleeping Dragon?"
He rubbed his chin, gave a relaxed smile, and drew his wand, circling it over his head as he murmured:
"Disillusionment!"
Like a chameleon, his entire body took on the exact colors and textures of his surroundings.
The sixth-year Ravenclaw walked easily past the Stone Dragon. Sure enough, he provoked no reaction and went straight inside.
The young witches and wizards around him sighed enviously, but the Disillusionment Charm was an advanced spell. Those capable of casting it were generally fifth-years or above.
Zhang Xiao looked around. Sure enough, almost everyone was below fifth year, with progressively more students from each younger year.
There were also plenty of first-years, who weren't allowed into the grand Common Room, standing nearby to watch.
Having more or less figured out Dumbledore's intentions, Zhang Xiao stepped forward and strolled over beneath the watching eyes of the other students.
If the point is to train the students, then besides clever tricks, stealth, and teamwork... surely fighting straight through should count too?
He spread his fingers, and his wand hummed as it sprang into his hand.
Tap. The sole of his combat boot struck the smooth floor with a crisp sound, as though he had crossed an invisible line.
The Stone Dragon's eyes snapped open. He shook himself, stretched like a living creature, and let out a long roar at Zhang Xiao.
He even has some detection ability? He knows I'm much stronger than that student earlier?
He was