Sorry <3 gotta do more explainy bits <3 i'm giving more context than is necessary because i love talking about this world so much <3

Downworlder: basically any mythical creature that's not a shadowhunter or a full on demon and are split into 4 categories. Werewolves—People inflicted by a demon disease to turn into a wolf. Vampires—people inflicted with a demon disease that are undead and drink blood. Warlocks—children of demons and humans, are immortal, and can use magic naturally. they always have a "mark" that sets them apart from normal humans that can be anything (blue skin, antlers, weird eyes, wings etc.) and Faeries—biggest group of mythical creatures and said to be the children of angels and demons. split into the seelie and the unseelie courts. All downworlders have been oppressed by shadowhunters because of the demon blood in them for many years and only recently through a treaty called "The Accords" was any sort of mutual respect started to come about.

Shadow Market: community black markets of sorts for downworlders to share their wares and gossip of sorts. Shady stuff goes on sometimes and shadowhunters generally aren't very welcome in them.