Myrddin himself ran the next stage in his process. His shaft furnace was just a tube of wattle and daub, vitrified by repeated firings. By the time Regina arrived the furnace had been running since early morning, and two more unfree were laboring mightily at their animal-skin bellows. They were naked save for loincloths, and their bodies were slick with sweat and soot. Myrddin was supervising the day’s first charge of charcoal and ore.

He preferred charcoal made from alder, which he said burned hotter than any other sort, and ocher, a relatively easy ore to smelt. The furnace would be worked all day, and then allowed to cool; by tomorrow Myrddin would be able to pull out a bloom, a dense, irregular mass of metal and impurities. This would be subject to repeated hammering and heating until the last of the slag was gone. It took several blooms for Myrddin to produce one of his ingots, a flat bar about the size of a sword blade, ready for further work. All this had baffled Regina—it seemed an awful lot of work for a small piece of iron—until Artorius had gently explained that even charcoal ovens were not hot enough actually to melt iron, and Myrddin’s elaborate practices were necessary to coax the iron out of its ore.

Though she despised the way Myrddin used his secret knowledge as a source of power, she could not deny the reality of that knowledge. Watching his careful, almost delicate work as he constantly inspected and assessed his furnaces and clamps, she thought she could see something of the centuries, or millennia, of trial and error and constant study that had led to the development of such techniques.

And the end product was iron, the most precious resource of all, pieces of iron that, remarkably, had not existed before. Piled up in Myrddin’s workshops were some of the final products of all this industry: carpenters’ tools like adzes and saws, tools for the farmers like harness buckles and sickles and reaping knives, weapons for warriors like swords and knives—and even tools for Myrddin’s own use, like tongs and an anvil. It was Myrddin’s proudest boast that he was the only craftsman who produced all his own tools.

But Myrddin was Regina’s enemy.

When he spotted her, he greeted her with a kind of snarling smile. “Here to check up again, Regina? Tap, tap, tap with your stylus . . . a shame we can’t eat your words, or nail our soles to our shoes with your letters, eh? But at least we can wipe our arses on your scrolls . . .” And so on. She endured it, as always, and walked on.

A young apprentice called Galba was working at a forge, and Regina paused.