A black magic black market where you can get things you can't get anywhere else.
The Running of the Gorgons.
Win Fame and Fortune in the Arena of Death!
A massive library run by an androsphinx.
There's a mystery cult in the city that worships a
mysterious god who grants bizarre powers.
The PCs learn the city is secretly run by:
- a clan of wererats.
- a cabal of warlocks.
- a dragon.
- an incubus who's seduced the Autocratix.
- the Beggars' Guild.
The PCs learn that the city's premier sage is actually
an arcanaloth in disguise.
The city is a port for skyships.
The city has gates to the City of Brass on the Plane
of Fire and the City of Pearl on the Plane of Water.
The city is a teleport hub, with circles going to
all the other major cities in the world (and possibly beyond).
One or more of the PCs' mentors/family members lives
there.
The PCs must travel to the city to receive an award
(title of nobility, deed to a parcel of land, etc.) they've earned.
The city is built around magical springs that flow
with enchanted waters.
The city is considered a neutral zone where
creatures of all alignments and from across the multiverse can meet and engage
in (relative) safety.
Neighborhoods of the city randomly shift into the
Feywild, the Shadowfell, or the Ethereal Plane.
The city is holding a tournament and the greatest
warriors of the world will be competing.
The city doesn't know it, but it's hosting a
death-match tournament between warlocks serving demons.
The city is having a festival of misrule, when
crimes are now legal and sobriety is punishable by being transformed into a
goblin.
The city is having a masquerade festival, where
everyone disguises their identity with masks and illusions and indulges their
most secret desires cloaked by anonymity.