The Masters of the Bazaar
"The Masters of the Bazaar - Mr Wines, Mr Spices, Mr Veils and the rest - speak in high-pitched whispers, and under their concealing cloaks they seem winged or hunchbacked. Fallen angels, stunted pterodactyls, mobile colonies of fungus[, ...bats]? They dismiss all personal questions with an airy wave of their gloved hands."
"The Masters apply peculiar customs duties: to fish below a certain size, to green ribbons but not red, to speckled eggs but not plain. Perhaps their strangest tax is a heavy duty on stories of love, but it only applies to stories leaving the Neath..."

The Masters of the Bazaar. It's hard to describe these cloaked, slightly creepy bat-people-things. They call themselves Mr., but they may not really be men. Confusing? Fallen London is generally that way...
Here is a list of the Masters and their domains. It is known that there are eleven true Masters, two pretenders, and one former (partially-destroyed) Master.
True Masters
Mr. Apples: This upstanding citizen governs commerce in food, wood and immortality. They say it's an ally of Mr Veils.
Mr. Cups: crockery, pottery, sculpture. His Relickers also will barter for valuable items. It runs an emporium in the Labyrinth of Tigers.
Mr. Fires: coal, gas, candles (this last one after the fall of the Third City and the partial destruction of Mr. Candles). It also controls the neddy men from his office in Wolfstack Docks.
Mr. Hearts: meats, bloods, puddings, and other animal-derived delights. It runs an emporium in the Labyrinth of Tigers.
Mr. Iron: Tools, printing-presses, guns, steam-engines: taxes from trade in these are payable to Mr Iron. They say it never speaks, but can write with both hands simultaneously. It also runs the game of Knife-and-Candle.
Mr. Pages: anything and everything written. It runs an emporium in the Labyrinth of Tigers.
Mr. Sacks: may control the bag trade, or something like that. He's also the new, much more demonic Santa - he stuffs people in his bag...
Mr. Spices: spices, sweet smokes, prisoner's honey, dreams.
Mr. Stones: jewels, quarrystone, salt, blasting powder... enough. It runs an emporium in the Labyrinth of Tigers.
Mr. Veils: Mr Veils deals with clothing and fabric, and takes a close interest in the silk-weavers of Spite. But not in any of the more dubious activities in the district of Spite! The mere suggestion is slander! It runs an emporium in the Labyrinth of Tigers.
Mr. Wines: Trade in anything drinkable comes under the jurisdiction of Mr Wines. Though it can't be bothered with water. Entertainment, music and the business of the ladies of the evening are also its domain. There's supposed to be some sort of dispute about dreams.
False/Former Masters
Mr. Chimes: Who is it? Is it, in fact, one of the Masters of the Bazaar? Is it Mr Iron or Mr Pages trading under another name? Or is it a bold rascal pretending to be an unknown Master? It runs the House of Chimes.
Mr. Eaten: Who is Mr. Eaten? A good question, but not a wise one. (Once Mr. Candles. Now a reclusive shadow of its former self. Part of an incredibly menacing storylet that is temporarily retired.)
Mr Mirrors: Who manages the House of Mirrors? Is it Mr Mirrors itself? Surely not. No Master would lower itself to become a carnival showman. But it is a sinister place. And it surely can't turn a profit.