Chambers
The corridor was long. Nero walked for a few minutes before he began to notice that the fog was increasing, with no end to the tunnel in sight. He sped up, going from a fast walk to a light jog.
He had to balance the dangers of rushing, with the dangers of being caught in the fog once it returns. Once the actual fog returned, Nero doubted that Neophytes would be safe. Or maybe they would. After all, the monsters living in the lower levels of the city had been alive for centuries at the very least.
Whatever the trick of their survival was, he didn't want to experiment with his own life, so he could only speed up.
Soon he encountered a sudden, sharp right turn, which would explain why the end of the tunnel was not in sight. Yet after he turned, while he did spot the exit, it was far.