Board Thread:Questions and Answers/@comment-155.69.191.254-20150116033651/@comment-16674955-20150116084653

Baam and Rachel are both irregulars.

The regulars are people who live in the tower (outter tower or middle area) and wait all their life to be picked by Headon to climb the tower, probably as per a contract Zahard made. It is assumed that Headon's choice reflects the tower's choices, therefore regulars are not "against the rules that Zahard imposed".

The irregulars enter the tower of their own, opening the door themselves. The people who were destined to be climbing the tower are those who entered it from the outside. The tower always chooses/accepts irregulars that it needs. Stability (Zahard), Change (Enryu), Revolution (I would assume Urek) and Liberty (Baam, supposedly).

BTW, if Baam wasn't an irregular, he couldn't have requested a test from the guardian of the second floor. Even though SIU left us in the dark about a lot of information on the tower and TUS, this is legit as it's the word of God.