So my memory tells me that prince is SUPER suspect. Or at least his bed buddy is, but we cannot point directly to him. Princes harem is called big and away from public eyes, so is he protecting them or are they the "Breeding Pit?" The Salamander is mentioned to be much 'bigger' then before, and one of the military officials mentions that he caught him bossing the maids around yelling about an important box (transformatives?) that was dropped or some such.
Princess seems the least corrupt, but I recall someone saying she was involved in the slums where we cannot go to to see what it is like. BUT she seems upset if you suggest assassinating the leadership of the demons. Seems to really want to focus on looking inward, it could be to sow discord OR just it the only thing her dad lets her do being stuck in the city.
King is already the king of the "biggest/best city in the north" but he seems to be recruiting all the strong/smart women into his harem and they seems to be becoming dumber, Mistress of the brothel seems afraid/worried for her friends that joined.
Senator is just a regular old politician imo, slimy sure, but does not really seem to be hiding anything. If you point out the water being odd he seems upset, but more so that his big political stunt might backfire, he wants to look into it.
Only the king and the prince have military power, the pullback to the city, the gap in patrols, and logistics of getting supplies and WATER. They both are also reported to be promoting the lax dress code.
The alter could be defiled by anyone with a dick really, but they would need access to the royal wing/hall.