The objective of the tower was to make the participants test themselves, be it mentally or physically, and possibly break their limits. All of the participants had to go through similar tests, and were advancing at their own speed.
From the outside, the observing cultivators were looking on nervously. The tower was the first test which they were unable to observe, as it contained things whose existence the Universal Government was not willing to share, or at the very least, not with those who could understand their nature.
What the observers saw from the outside, were red lights that shone through the tower's walls. Each light indicated the presence of a cultivator, as well as the floor in which they were currently staying.