User blog comment:B214/Question and Answers 6/@comment-187.180.176.223-20190619153726/@comment-36523287-20190620021927

The noble house and 72 Pillars house are different things. There are other noble house which isn't a part of 72 Pillars.

The author never clarifies whether reincarnated devils, who are promoted to an ultimate-class, can establish their own noble house or not. However, in the feudal system, the allegiance of one noble is pledged to the lord who give him/her territories. Since ultimate-class devils can receive a part of the Underworld from the Maou (Vol 5.), they should report directly to the Maou as well, not any other nobles. In that case, I think it makes sense for ultimate-class devils to possibly have their own noble house.