Volo's Student's Guide to
Cerilia
Everybody here is royalty. Everybody. Unless you work for royalty, but you wouldn't have the money to come to Sigil Prep anyway. Probably, if you meet somebody from Cerilia, and they aren't royalty, they're a Follower under somebody's Leadership feat. Maybe a Cohort, if they have any skillz.
Politics are a big deal here. Politics and large scale war. If you haven't taken Mass Combat classes, forget about adventuring here. You don't have the right rules set.
(see also: Urufu)