When she's descended, she finds herself in a massive vault. 

"You know, of course, that the Bazaar is engaged in the collection of love stories." It pronounces the phrase with distaste. "Did you ever wonder where it stores its rejects?"

It raises the lamp, casting light across the walls. Not walls; bookshelves. The nearest shelves are filled with clay tablets; farther away there are scrolls; in the distance, books, followed by empty shelves.

A bitter edge creeps into its sibilant voice. "Once a suitable love story is found, it’ll be the end of London. Can you imagine?" The lamp trembles in its hand. Its voice rises an octave. "The end of London! I couldn't bear it! I love this city. It's my sole comfort, the greatest joy I have discovered in all my centuries. I'd do anything to preserve it."

"Did you get moon-milked about it?"

"Of course not. The milk wears off after only seven years - a blink of an eye, for one such as myself. No, my love for London is true. It is pure. I love this city because it is beautiful. Everyone in this city is burning something. Candles, gas, souls... The weak are burned; the strong burn themselves."

"You visited my Orphanage, you saw my moon-milk research." It isn't a question. "I was hoping to use the milk to bankrupt London of love stories. It proved insufficient. It is not a convincing forgery, and it does not persist."

They walk past dozens of bookshelves. The clay tablets give way to scrolls. Bats nest among the vellum; a swarm explode from one of the shelves, momentarily enveloping the platform in a screeching, seething mass of wings.

Mr Fires waits for the bats to return to their nests, tapping its foot irritably. "The Hybrid is a more promising prospect," it continues. "Based on prior research and prior hybrid attempts, its milk will be more amenable to human digestion. It will be able to create something indistinguishable in all meaningful ways from true love, fierce, firm, eternal, consuming; as unbreakable as the bond between Romeo and Juliet or between mother and child."

"...I have so many problems with that I almost don't know where to start. But let's go with practicalities, since I can't see you giving a shit about ethics. You don't think people suddenly falling in true love with random lampposts and rocks isn't going to be distinguishable?"

It smirks. "Please. I intend to control the dosing strictly, not simply pour milk into the water supply. By the time the Bazaar realizes anything out of the ordinary is going on, it will already be too late."

"And you don't think the Bazaar will just stop you and wait for a new, untainted generation."

"The Bazaar cannot afford to wait. And certain other aspects of my plan mean it will not be able to simply destroy the city as it has the others; it will be forced to find a new home for its next city, and leave London in peace. Certainly it may choose to topple a few buildings on its way out... but London can rebuild. London has always rebuilt."

"Okay. So if London rebuilding isn't an obstacle, how about I just ask the Bazaar nicely to give me warning to evacuate everyone before it takes another city. I was going to do that anyway because I value human life, and I bet it will, it loves me."

It scoffs. "As if the Bazaar will give you such advance warning, when the deal cannot be predicted and must be struck the instant it is ripe. As if you will still value human life once you are grown. Indeed, as if London becoming a city of love would be so terrible!"

"I will always value human life. And mind control is bad. And taking babies away from their mothers is bad. If saving the lives of London is more complicated than asking nicely for warning then I will do something more complicated. I will not help you kidnap a child. Which would be stupid anyway. How would you raise them? They're not going to be just an inanimate venom-dispenser, you know. They'll be a person, and you didn't just crossbreed with not a moon-miser, you crossbred with a human. Humans aren't just a dilution of the blood of whatever you cross them with, you know. I'm not just the Mountain of Light but lesser. The Mountain sits on the Elder Continent and does not meddle. The Sun sits in the sky and does not meddle. The Bazaar sits in the middle of London and meddles comparatively little. I was introduced to this city a few days ago and have already done a hell of a lot of meddling. Humans bring agency to the table."

Fires shakes its head. "'Mind control'. What a human term. Love is arbitrary; it is not worse to be in love for a reason, no matter what the Bazaar thinks. And I will raise the child with all the love it is due - it will need it, to produce the best milk. And, to your other point, I care not for its incubator one way or the other. She can return to her former life, or she can help to raise the hybrid, as she likes. If this is not enough to convince you, I can promise you a reward. I hear you were after a particular diamond?"

"I heard a rumor about something I thought might be my sibling, that turned out to be the moon-miser, which I have already rescued. You cannot bribe me with shiny rocks. I imagine you couldn't bribe me with shiny rocks even if I wasn't made of shiny rocks. Whether or not it matters whether love is natural or not I do not remotely fucking trust you with the heart of a goldfish, let alone everyone in this city."

"Your sibling. I suppose that is one way to look at it; you were both liberated from the Mountain of Light. In which case... I have your sibling. If you give me the hybrid, I will give it to you. Does that tempt you?"

"Is it a person."

"Naturally. It does not have much to say - the imprisonment of an innocent being, usually, or a reckoning which will not be postponed indefinitely. It grows tiresome, frankly; I would be glad to have you take it off my hands. As long as I get my hybrid."

"You are not going to get anywhere near the child which you created without the consent of either of its parents." 

"Short-sighted of you, but not unexpected. I will still provide you with the moon-silk, as I am not best served by the loss of the child; it will be delivered to your mother's home by my assistants Jasper and Frank." It turns to lead her back to the entrance.

"Short-sighted of me," she hisses. "You have--absolutely no idea, do you? You don't even think you've done something less wrong than what you're trying to prevent, you don't think you've done anything wrong at all, do you."

"In time, if you live long enough, you will see. The humans lead their brief, human lives, and it is not worth caring for each individual one. Only en masse are they capable of greatness - as in the case of London."

She roars at him, a single and unprecedented word of Correspondence. 

THE HEARTFELT, BONE-DEEP BELIEF, PERMEATING EVERY CELL OF ONE'S BODY AND EVERY WISP OF ONE'S SOUL, THAT EVERYONE, NO MATTER THEIR PLACE ON THE GREAT CHAIN OR IN SOCIETY, OUGHT TO EXIST WITH HAPPINESS AND SELF-DETERMINATION.

Fires hunches down to weather the blast, mantling its wings before its face. Then it straightens, and its eyes are sad.

An acknowledgement that the referent is young, and that youth is a time of hope and righteous conviction, it returns. Experience gained over thousands of years of servitude to one who swore falsely that all would be well. An old wound that has festered into a system of belief.

...That stops her. 

Sorrow for the sadness of the referent. Acknowledgement that the universe is a place that contains a great amount of suffering. The firm conviction that the ambient quantities of sorrow or joy in the universe do not make the sorrow or joy of any single person less important than if they were the only person in the universe.

"I do not desire your pity," Fires hisses, and continues walking. "Suffering is inevitable. It can be directed, and harnessed, but ultimately, to stand tall, you must stand on someone else. You will one day come to terms with this truth... or it will break you. Just as surely as it broke Wines.” 

The subtle yet critical difference between sympathy and pity, she retorts, and, thoughtfully, "I guess I'll have to talk to Wines for their perspective, then."

Fires snorts. "Ask who you like. Seek out what remains of the Runt and ask it, too, I'm sure it'd have a fascinating perspective. But make sure you've put your affairs in order, beforehand."