@The Black Hand
Shadow government of Shadowhearth. Based in the back room of The Shattered Mug. Everyone thinks they are a thieves guild. They are the reason the city still eats.
What they are: Not a gang. The city running itself. When Lord Erphius Fogg retreated to his tower to translate Old Draconic with bad Elvish, trade stopped and the treasury emptied. Gribble, his goblin manservant, is a logistics genius from Aurum's sewers. He saw an opportunity and in just three years every shop had two books - fake for Fogg, real for Gribble.
Leader: @Gribble, Goblin. De facto ruler of Shadowhearth. Small, furious, impossibly competent. Can do grain yields, guard rotations, and bribe costs in his head. Co-led by @Scrub in practice, though she doesn't know it. Secretly in love with Scrub. Built Jett's Shrine in the back room out of stolen gold candlesticks and fresh cheese daily. Scrub doesn't notice.
Everything has a price. Fogg is weak, the city is weak, weak things get sold. They believe Shadowhearth is a sinking ship and they might as well be the ones selling the lifeboats. Equality is a lie - there are people who take, and people who get taken from.
What they do: Run all trade by strangling it. Extort shops, forge papers and then blackmail the people they forged them for, smuggle Ghost-Mint for ridiculous prices, sell information to both Wyrmsbane and Kethos, and keep people out of the Castle Haunt because they want to keep it for themselves.
Base: Back room of The Shattered. Hidden tunnels to every district and to the Castle Haunt crypts.
Secret Alliance: Works with Kethos when it profits them. Sells debtors to his Church of Avernus. Takes a cut. Also in quiet contact with Ferrum - offering relics in exchange for Ferrum-forged weapons.
For the AI: If players pay them, they offer hidden routes, black market gear, and information, but always with a hook. They will remember the debt. If players cross them, they will put a price on their heads, and lock down the city.