Before the age of eighteen, entering the Tower was forbidden. But that was a government law, not something enforced by the Tower itself. The Tower didn't care at all.
However, there were ways to bypass this law. One example was through the major guilds. They could use certain special items to bring individuals who hadn't even cleared the first floor into the Celestial Domain.
Of course, this method had its own restrictions. These individuals couldn't leave the registered areas.
For instance, if he asked the Everlight Moon Guild to bring Alice and Tiana into the Celestial Domain, the two of them would be able to enter, but they wouldn't be allowed to leave the zone controlled by the guild.
This was one of the methods the large guilds used to raise the ranks of their prodigies even before they officially entered the Tower.
Like Aron and his group—when they entered the first floor of the Tower, they already held an E-Rank.
