I think those slaves belong to another empire. Some of his species (thise with wings) are those that are from the weakest empires.
Per the spoilers I read,
because Celestials are weak that's why everyone looks down on them.. this Manhwa has so many skipped parts on the novel.. they are ranked 1 because they have raided or on the top floors of the tower.. they are way above the tower floors than the other players they became strong because MC changed their attributes to Dark Celestials..
So MC and the slave guy are both celestial race but do not belong in the same kingdoms. Like for example, there would be an elven race but in the elven race there different branches like dark elves, light elves, nature elves. Etc etc. Originally, MC was a golden celestial or was heavnly celestial, idfk remember but he recently changed their race to dark celestials. Later on, we'll see other types of celestial races.
Enslaved guy is actually a king himself cus the ONLY ones who can enter on the same room in the party as MC are other kings from different kingdoms(their dukes are on the second floor as observers). It was explained previously but it's hinted that the slave guy is in an unfair contract with one of the kingdoms invited into the party(huge hint, it's one of the people harassing him durong the party)
where did you read the novel?
So is his empire still ranked 1st? And if so how is it that there are slaves of his empire? Or how everyone looks down on his empire??? Also mister froggy is so cute! (Lemme guess giving a feather means something)