A secret world of magicians/witches. Ghosts, werewolves, and vampires, oh my! Gods and goddesses, mermaids and lamias.

There is a society of vampires who struggle between the impulses of tradition and modernity- very few of them want to care about human life.

Werewolves, meanwhile, while they do form packs, tend to care very little about whether they might hurt humans, yet still see themselves as better than the monstrous vampires. Born werewolves often need drug treatments to manage the mental health consequences of being stuck as a human so much of the time- and some of them do this more responsibly than others. Bitten werewolves, meanwhile, die alone or find packs.

Ghosts wander the Earth, invisible to anyone but vampires, werewolves, witches, and mediums. They have unresolved issues, and are often tied to the place they die. If they begin to resolve those issues, they will find their door, which probably leads to an unknown afterlife. If they try to stay, they will be more free to leave their place of death, and can learn abilities such as possession- but possession is addictive and can damage the victim's mind, and staying on Earth too long has mental consequences for ghosts, too.

Mediums can see ghosts, and can reincarnate ghosts into newborns. There is not enough evidence to be sure this is a bad idea.

Werewolf blood smells disgusting to vampires, but it has psychoactive properties. However, it is toxic enough that they inevitably expel it, and it permanently changes their ability to turn new vampires, instead producing hybrids thereafter. Any human they turn from then on will instead become a horribly ugly hybrid with even greater control issues than vampires (though those that survive the initial rough patch discover a much more powerful ability to glamor). Werewolf blood also inoculates vampires against some vampiric diseases.

While vampires struggle to maintain their hold over the underground of the city, werewolf packs live their lives unconcerned with human or vampire law. Meanwhile, ghosts wander the Earth until they can resolve their business and move on. Witches do magic. Mediums sense ghosts, perform exorcisms, and reincarnate ghosts. Once the qualities of werewolf blood for vampires are discovered, there are also hybrids.

-The underground vampire government has politics.
-Vampires can glamor people. This can have consequences, since it's not completely foolproof.
-Werewolf packs are hotbeds of violence, and they tend not to much respect humans or vampires.
-Vampires find werewolf fighting pits an entertaining diversion.
-Ghosts can possess people, which has unpleasant mental consequences for both ghost and host.
-If a ghost passes on their door, they get more powerful, but this has mental consequences.