This is a secret of the Ninth, she says, and immediately Wei Wuxian sets down his pen. To guard it as closely as she wishes, he will not leave a written record.

As she describes the method for growing bone, though, a crease forms and deepens between his eyebrows. Not for the first time, he is struck by her brilliance, how her necromancy operates on a level far above Wei Wuxian's own. He has the same sense one would get when sprinting breathlessly after someone so much faster: he will catch up, eventually, but the faltering in between lights a tiny spark of frustration.

"So," he says slowly, trying to parse what she's said. "The new bone you are able to grow acts as a reservoir, nearly. But only because it is constantly changing as it grows. I may be able to hold onto the thanergy if I can do something similar?"