Xylar obviously. But being serious, the cabal must have someone at the top which would make that like the king or somthing so te cabals King. There are also many other hive gods aside from oryx which would make me assume that oryx has family out there that are stronger then him. We stopped atheon but there are most likely other vex time gods out in the solar system, Mercury would be the best bet considering the vex pretty much own that place aside from the lighthouse.