I do not even remember him going on a dungeon, in any case there is one OP ship but another reincarnator gets it, to her bad luck it is not as nice as luxion. Leon will challenge that jerk who took his stuff to a fight and then Luxion will simply use everything to attack the jerk's country under the jerk's name and win! That is what i remember from the novel.
Luxion is just faking switching sides, he is pi** with Leon but he can't really switch sides because he serves old humans, not the new magical ones. I can't remember exactly if Leon knew about the fake betrayal. but they used it to extract info and make the families make mistakes.
