“Harrowhark, think,” he said, which reminded you very unwelcomely of someone. You gave your thumbnail a better edge, sharpened the dead keratin to a point, and finally drew blood. “What else has an enormously complex mass of thalergy? What’s the role of a Cohort necromancer?”

Your brain bowed out disgracefully, but something of the old Harrowhark remained, enough to stand there and ask questions. You were grateful for your impertinent ghost-self to ask: What was the role of a Cohort necromancer? Better to ask the purpose of a Cohort swordswoman: to support the necromancer, to provide the death and the thanergy to begin the cycle for necromantic magic to work. Foreign planets were never thanergy planets; they possessed dilute thanergy, of course, but fundamentally they were thalergenic in character. Send a necromancer down there and she would be largely useless. Thanergy really came from—

More to the Body than to him, you said: “A planet’s a ball of dust. Its thalergy comes from the accumulation of microbial life. You can’t consider it one coherent system.”

“Call it a communal soul,” said her Emperor. “What’s a human being, other than a sack of microbial life? You’re a bone adept, aren’t you? Flesh magicians are exposed to this idea of a system earlier than in your school.” This was kindly, even humourously said, but you still found that you immediately wanted to be tossed out the airlock at the idea that your aptitude made you less than a flesh magician: someone whose entire education was in the carnal. Experts in things that were yellow, and wobbled. People who thought there was something really interesting to be found in meat.

He mistook your deeply bigoted hate for disbelief, and said: “Just accept the proposition for now that a planet has an enormous single amount of thalergy. If this thalergy is converted, what might happen during that transition?”

“We already know what happens,” you said. Your tongue was growing thick in your mouth, and your eyelids were sore and swollen from wanting to close. The first rush of adrenaline had run its course. The Body came and took your wrist in her hand and ringed her fingers around your bones, quite tightly. This let you say: “The Cohort prepares a planet for necromancy every time they have to breach it. Over time, with the introduction of thanergetic decay, the planet converts. Necromancy proceeds as normal afterward. Nothing happens … plant and animal life both change, of course … and eventually the planet flips totally and the population has to be moved, but that’s such a long-term process that it takes generations. You can’t quantify it as something happening.”

“Now kill the planet all at once,” said her Emperor. “What then?”