User blog comment:Pualover/Overlord Power Level/@comment-96.227.219.59-20150928193147/@comment-26980003-20150928194136

It is assumed by the LN readers that Rubedo's level is 100. Since it stated in the last translated volume of the series that Rubedo is the strongest being in Nazarick basically, she would have to be level 100 in any case. Gargantua's level is still unknown. But it is known that its really strong as well. Could be a low level like victim or a high level 100 like all the other floor guardians, with the exception of Victim.