For the plan to work, Zorat had to make certain the enclosed space was unescapable. He was already done with the first part, which was responsible for getting himself and Erica down here. Now he had to seal the place tight.
The first part was simple enough. Zorat had set the inscribed portal at the top so that, with just a mental pull from him, it would drop both himself and Erica into the receiving end on this hundredth floor, using his mental strength, of course, and the setup would also spontaneously disintegrate upon the transfer.
The latter part was not needed really, since no one would even know what they were seeing when they looked at the markings. But since Zorat was not certain how many more times he would use such a strategy, he decided it would be better not to leave any calling cards hinting at curious folks in his direction. What fun would it be when everyone starts knowing all your moves ?.
