The powder was metal. The metal was Yin Iron.

These two thoughts chased each other through Wei WuXian's mind in an endless loop, as he fought to force down his surprise and breathe through the shock. Metal. Yin Iron. Metal. Yin Iron.

Yin Iron.

How was this possible? Yin Iron was so vanishingly rare, so little remained in existence, after destroying the Yin shards in Wen hands, and his own destruction of his Yin Iron Amulet. Where had it come from? Who could reduce it to powder? Why hadn't he noticed the feel of Yin Iron being nearby? Was his system so occupied by pain it had hidden the tell-tale tang from him?

Wei WuXian's mind spun dizzily, filled with questions that spiralled endlessly. He barely noticed when the now-familiar midday routine of pain ramped up until it took control of his body once more, leaving him heaving and helpless on the floor of his workroom as he spewed into a basin. Time slipped by unnoticed as he struggled to manage, finally laying flat on his back, spent on the floor of his workroom. Gradually the pain began to recede, the nausea to lighten. Over time his thoughts took on cohesion again. He lay weakly where he sprawled, looking up at the ceiling.

How could the metal be Yin Iron? Why had the pain in his nerves and bones responded so strongly to the touch of the Yin Iron powder? Wei WuXian touched his Core and sent the energy drifting lightly through his Meridians, his Qi following familiar pathways. The singing and humming of the Dual Cultivation were no longer noticeable, but the pain that constantly buzzed along his nerves these days was stronger, more insistent, as if it resonated to the resentful energy that so recently flooded through him. He concentrated and drove down the resentful energy remaining, and flushed it from his system, forcing it to dissipate and filter away. The pain took on a lighter note as he cleansed his tissues of the dark energy. He wished he had ChenQing in hand. It would have been quicker. He was too weak to go seek her, however, and to weary to demand her presence to him, so he lay there on the floor and used his hard-won skill to force the resentful energy from his flesh and release it.

Wei WuXian dragged himself back upright. Haltingly he cleaned up his workroom, placing the dish with the powder from pellet 6 carefully in the centre of his desk. He needed to share this discovery with Lan Zhan and Lan XiChen, yet he was afraid to do so. What does this mean? Who could possibly be capable of manipulating Yin Iron? His mind overflowed with questions. As far as he knew, only he and the ancients had ever successfully forged Yin Iron, and his own discovery was born of soul-deep desperation, elemental survival instinct, and took three months on the very knife edge of death to manage. Who else could bear the experience? Survive it, even? Why? Why would anyone create this horrific tool? And why unleash it on Lan QiRen? What if it wasn't just for Lan QiRen? Where else could this evil material have been deployed? How many other people might be lost to inexplicable Qi deviations? That weren't legitimate Qi deviations at all?

Wei WuXian held his head in his hands, elbows on his desk, as he struggled to rein in his thoughts. Questions. More questions. Nothing but questions...he shook his head. Enough. He had to get word to the Twin Jades. Taking to his feet, Wei WuXian realized he was weaker than he'd thought. His knees shook as he made his unsteady way to the door of the Jingshi. He would never get to the Hanshi or the Lanshi, to either of the brothers. He sat at the edge of the landing entry to the Jingshi and waited until he saw a disciple pass nearby.

At last, a flicker of white robes at the far end of the courtyard.

"Hello," he called, waving his arm for attention. "You there, can I borrow you a minute?"

In a moment the disciple came nearer, and Wei WuXian recognized the young man, who bowed and said, "May I be of service, Master Wei?"

"Thank you... JingYi, is it?" asked Wei WuXian.

"Yes, Master Wei. I am Lan JingYi."

"JingYi, would you please be so kind as to pass a message to ZeWu-Jun and HanGuang-Jun for me?"

"Certainly. What is your message, Master Wei?"

"Would you please let them know that my research has provided results that bear discussion, and ask if they could please come here to talk about things? I hate to interrupt them, but it's important."

JingYi's expression was skeptical – very little could possibly be more important than anything ZeWu-Jun or HanGuang-Jun chose to do – but he was well trained. Although his lively face betrayed his thoughts, he kept them to himself, and simply bowed with a polite "Certainly, Master Wei. Immediately," before he turned and swiftly walked away.

Once alone, Wei WuXian used the sturdy railing to drag himself back to his feet. He wobbled indoors and set about making tea. He really wanted some Emperor's Smile, however tea would have to do for now.

In the Hanshi, Lan XiChen received the message while working on correspondence. WuXian's found something, he thought to himself. He'd not ask for me unless he had something. Filled with fear and hope, Lan XiChen finished writing the letter he had begun, then tidied away his work and rose to make his way to the Jingshi.

At the Lanshi, Lan WangJi received the same message mere minutes later. Calmly he rose. Selecting two senior disciples to supervise, he dismissed class for the day and sent the disciples to the Training Grounds to drill on Lan sword forms. In a swirl of white robes, he left the Lanshi, moving swiftly toward the Jingshi, where he met his brother as they arrived at the entrance together.

As they entered the Jingshi, Wei WuXian looked up with a smile, to see the brothers silhouetted in the entry.

"Come in, come in!" Wei WuXian welcomed them. "I've just been making tea so we can talk about things. Have a seat." Waving the men to seats at the table, he poured tea and passed the cups to Lan XiChen and Lan WangJi. Lan WangJi looked carefully at his husband, taking note of the shaking hands.

"What is wrong with Wei Ying?"

Wei WuXian looked up, a feeble laugh trailing away as he caught his husband's eye. Looking away, he shrugged. "Nothing, Lan Zhan. I'm fine."

Lan WangJi was not so easily put off.

"Do not tell falsehoods." Gold eyes sharpened their gaze. "Care for one's body. Seek help when required. Accept concern with grace."

Wei WuXian held up his hands. "Aiya, Lan Zhan, enough already! Stop hitting me with the Rules! I'm fine. I just found out something that took me by surprise is all. No need to worry. I'm fine, just a bit shaken up." He put one hand over his husband's, rubbing small, comforting circles on the back with his thumb. "I'm fine, my love."

"Mn."

"The message stated that you had found some results in your research, WuXian," started Lan XiChen. "I'm glad to hear you are well, but may I ask what you've discovered?"

Wei WuXian turned to the Sect Leader, his face grown quiet and serious.

"The pellets we found in your uncle's home..." he began.

"Yes...have you determined what they are?"

"Not really, although I think it's probably a safe assumption that they were provided in the guise of a beard supplement of some type. But I've been looking into the powder all morning. Not too long ago I was able to confirm that it is definitely powdered metal impregnating all the pellets."

"Powdered metal? You're sure?"

"Yes."

"How odd. Why would anyone feed Uncle powdered metal? What would be the purpose?"

"I spoke with the Healing Hall. Metals can be used to poison, but I don't think that's the case here. Or not exactly the case. Apparently metal that is refined finely enough, into particles small enough, will be trapped in the body's tissues when consumed."

"What would be the point of that?"

"Well, with other metals I wouldn't be too certain, but in this case, I suspect this is what directly led to the retention of resentful energy in the Grandmaster; enough of it and for long enough to send his Qi out of balance. It would not have required much."

"How is that possible? How would it even happen?"

"I think whoever sent the pellets knew of the Grandmaster's particular weakness for his chin hairs – let's face it, his beard has been a famous indulgence since long before I was a schoolboy – and used that to their advantage. I think they made up these pellets to look like a beard supplement and used them as a vehicle to have your uncle ingest the metal powder. The pellets dissolved inside your uncle, depositing the metal powder. The powder was fine enough to be trapped and enough accumulated for it to do as they planned. The whole reason for the metal powder was to draw in resentful energy and provide an anchor for it within Lan QiRen. I think the Qi deviation is the result of the resentful energy being locked into your uncle, interfering with his ability to manage his Core and Qi."

The brothers looked more alike that ever, twin expressions of shock and horror on smooth faces looking back at Wei WuXian.

Lan XiChen broke first. "Were you able to discover what kind of metal was used? How could any metal draw forth resentful energy and lock it in place?"

Drawing a deep breath, Wei WuXian sat back on his cushion.

"I was."

Another breath, just one more before he turned their world upside down... but it could only be delayed so long.

Carefully Wei Ying set his tea cup down and looked into Lan XiChen's eyes.

"It's Yin Iron."