Rulers (지배자, Jibaeja, "Rulers") are the overlords of a Floor in the Tower. They are always someone of a level equal to a High Ranker. They may be referred differently, depending on Floor ("President", "Boss", "Chief" etc.). Rulers gain the authority to rule a Floor with the permission and consent of the Guardians. Since most of the Floors were conquered by Zahard and the 10 Families, most Rulers are affiliated with the Zahard Empire. However, it is worthy to note that of the 134 conquered Floors, only two are ruled by a High Ranker that is not a member of one of the 10 Great Families or the Zahard Family. Those Floors are the Seventy-Seventh Floor ruled by Baek Ryun and the Second Floor ruled by Evankhell. Also, there are two conquered Floors of the Zahard Empire with no Rulers. Such Floors are the First Floor, whose only inhabitant is Headon, and the 43rd Floor since the Floor's Guardian was killed by Enryu and a Ruler cannot rule without a Guardian.
Since the authority of a Ruler is granted by a Guardian, they cannot act against the Guardian's wishes. Though the Ruler currently manages the tests of a Floor, that doesn't mean that the Guardian's authority has wavered. The Ruler (and therefore their subordinates) are only acting on the Guardian's behalf. Despite the power and influence of the Zahard Empire, all staff (including the Ruler) on the Floor are still subjected to the Tower's rules in the testing Floors of the Inner Tower.
Also, the Ruler has the right to make absolute decisions in regards to the tests on their Floor. However, if the Guardian objects, the Ruler must obey the Guardian's wishes, because all rules that were created by authority of the Ruler of the Floor and his subordinates are completely meaningless in front of Guardian and his dictates.