Reaching out with her left hand, several papers split off from Yao's arm and wrapped around the chunk, bringing it closer to her. She silently inspected it for a few moments, subjecting it to four separate talisman-based tests. Twice, the paper's patterns changed colour, and twice more, it burned on contact with the stone - the first time was instant, like flash paper, and the second slowly blackened the paper as if the charcoal piece was just a hot ember. After contemplating for a further minute, Yao simply asked: "Are you yourself aware of what this is?"

"Yes," Krahe nodded. "I'll make this simpler for the both of us: I will not reveal how much I know - and from what perspective that information comes - until you do the same. I believe we can both benefit from an exchange of knowledge."

After a few more moments of contemplation, Yao took the chunk in hand and began speaking.

"This is... Well, there is no direct equivalent word that comes to mind."

"Charcoal?" Krahe suggested. It looked like charcoal, so she wasn't giving up much by suggesting that word.

With a nod, Yao continued: "It is charcoal made from a human, body and soul both. In Tiengenzhen, this is the 'waste', or perhaps more accurately 'side product' of the Onyx-black Puppet Hall's human refinement arts. Even this 'waste' is considered immensely valuable to all artifact cultivators, as it is the cheapest fuel for certain artifacts and tools. Its value is such that inferior versions of the Onyx-black Puppet Hall's rites have spread throughout the land, only capable of producing this. The strongest battle puppets devour a hundred convicts' worth of this in a day of operation, but they are still used by the mortal kingdoms because the number of lives they save far surpasses the price. Even so, it is..."

Turning the chunk around in her hand, Yao's expression shifted from one of consideration to disgust, and she put it back on the table.

"Wretched. Human refinement is, by its very nature. The victim's suffering is part of the process, it does not work without it. I believe the Onyx-black Puppet Hall's method is called the Five Torments Blast Furnace Refinement, involving a specially constructed 'furnace' chamber that deprives the victim of all senses, keeps them alive, and allows for the introduction of hallucinogenic poisons throughout the process. Only reincarnation ends the victim's suffering, despite the rumours of the uneducated that claim the victim's soul is imprisoned in the coal. That is my understanding of this substance, its origins, and its uses. Now, I believe, it would be your turn."

Digesting the information, Krahe started with an easy one: "This Onyx-black Puppet Hall. Are they related to the Thousand Puppets Hall?"

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"I am surprised that you are aware of them. Yes, they are related. The Onyx-black Puppet Hall was formed by a group of demonic artifact cultivators who left the Thousand Puppet Hall rather than let themselves be judged for their crimes. I must ask, if you do not mind, how do you know of the Thousand Puppet Hall?"

"I saw a man with strange-looking arms, looked into the matter, and learned that one of them was of Tiengenzhen origin. Not much else, unfortunately. Now, regarding what I know of this stone..."

Krahe went on to recount some of her knowledge regarding human charcoal and the Human Charcoal Cults, taking care not to stray or to go too deep, so that the knowledge she shared would not surpass what Yao had shared, or otherwise reveal what she wanted to keep concealed. The talisman mistress gradually became more visibly interested, particularly at the mention of the Human Charcoal Cults.

"You would not happen to be aware of when these cults were active, would you?" Yao asked.

"At least a century, starting in the late 4120s. Presumably before that, but I don't know enough to make any guesses."

A smirk took hold on Yao's face.

"What a curious coincidence," she chuckled. "An acquaintance of mine made off with copies of the Onyx-black Puppet Hall's ritual scrolls only thirteen years prior to that time, and vanished from Tiengenzhen in... Oh, I think it was 4112. But he would've left inheritances, that bastard was not the sort to put all his eggs in one basket. Perhaps the church was just very thorough."

"And perhaps they still take such great care specifically to curtail cases like Sorayah. Even what she found was enough to sow the seeds of a serious issue for the city, given how well they paid me for rooting her out."

Knowledge of Sorayah and the fact Krahe had dealt with her was the smallest thing here. It was convenient to use as a framing device for how she had obtained human charcoal and knowledge of it, and she hadn't spoken so much as a word regarding the Hexkey or the Anthrocite Hand.

Nonetheless... This game was still frustrating. After some further circular conversation, Krahe decided to just ask the question outright: "Considering everything, do you think human charcoal would be of any use to either of us?"

"No," Yao said without hesitation, shaking her head. "Too volatile for ink, or any other artifact crafting. Its only use is as fuel for artifacts and certain demonic rituals, of which I know a few, but none of which would be useful. There is a good reason it is considered a borderline waste product. The energy output by its burning is far too unstable to use in the manner I desire, and besides sheer burst output, your own natural abilities are superior to the burning of human charcoal. Its greater counterpart, however, is another matter."

"What if I happen to come upon it?" Krahe asked, allowing her tone of voice and expression to make it clear she had anthrocite or knew where to find it. "You wouldn't happen to know and be willing to share methods of distinguishing it from the chaff and making use of it?"

"That depends on the quantity, quality, and use case. I do not own any written texts, but I am certain I could aid in preparing and performing any channeling rituals."

Krahe weighed her options. There was the chance that the Hexkey's evolution would turn out not so useful, and either way, Yao was still one of a vanishingly small minority with reason to not screw her over and the skills to craft a higher-order voidkey. If she kept this course, she would have to eventually disclose the Hexkey's existence to Yao regardless.