Only gold, silver, and weirwood, were magically conductive enough to power runic enchantments with ambient magic nearly forever. Permanently enchanting other materials was a pain in the arse without a living sacrifice. But everything else required sacrificial magic. Or as it was called in this world-blood magic. An animal could always be used as a sacrifice to power the enchantment, but they were quite inefficient. He had to sacrifice a score of bears to gain the same effect as sacrificing a single human, which was quite impractical. There was a reason why the Valyrian Freehold used blood magic so heavily with millions of slaves on hand. With enough lives, almost anything seemed to be possible. And lives were cheap in this world.