I smile despite myself at the proud flick of her neat lynx ears. Tien has worked for us for as long as I can remember, more family now than shop hand despite our caste differences. Because of that, sometimes its easy to forget that there are differences between us. But while my father and I are Paper caste, Tien belongs to the middle caste, Steel. Somewhere between my plain human body and the animal-like strength of Moon castes. Steel castes have elements of both, making them a strange meeting point between human and demon, like a drawing only half finished. As with most Steels, Tien has just touches of demon: a tapered feline maw; the graying amber cat's fur wrapped around her neck and shoulders, like a shawl.