Basilisk
The basilisk slithered through the pipes. He'd nearly been caught in his attempt to kill a few times. And he hadn't even managed to get a kill. Yet. That would change. But he couldn't afford to get caught so he'd slithered away from Hogwarts.
He looked out. What is that? He wondered. He was looking at a glowing circle that was impossible to see on the other side of. Well, there's one way to find out. He slithered into it, which was pretty easy, it practically sucked him in. on the other side there was some sort of wall, made of rocks. He broke right through with his huge size.
This place was very different than where he'd just come from. Maybe here, he could kill.