He almost missed it.
He had moved to the natural history volume after the theoretical texts — less useful for immediate application, but the gaps in his knowledge of the world's magical species were gaps he wanted to close, and the natural history had a systematic catalogue of demihuman tribes that he had been wanting since before Saya arrived. He read the fox tribe entry carefully, cross-referencing what he knew from Saya against the scholar's account, and found it mostly accurate with some details wrong in the way that outside accounts were always slightly wrong about things observed from the outside.
The eagle men were three pages further on.
He had been scanning. He stopped scanning.
The entry was half a page, illustrated with a line drawing that was clearly based on a secondhand account — the proportions were slightly off, the wings drawn more like a bird's than what the text described — but the text itself was precise. Aquiline demihuman, the scholar had written. Predominantly mountain and high forest territory. Physical enhancement affinity similar to other demihuman tribes but organized toward aerial capability — the specific musculature for wing-powered flight, the bone density appropriate for size-to-strength ratio, the sensory adaptations of a creature that navigated three-dimensional space at speed.
The wings, the text specified, were large. Proportionally very large. Wingspan of three to four times the body height at full extension, necessary for sustained flight at the weights involved.
He read it twice.
Then he looked up at the ceiling of the library reading room, which was about fifteen feet high, and thought about the specific feeling in his previous life of looking out of a plane window at thirty thousand feet and thinking: I want to be outside that window.
He pulled his notation book from his spatial pocket and opened it to a blank page.
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Winged Flight, as a magical problem, was interesting.
He had two main flight spells already — a simple anti-gravity construct that lifted the caster and propelled them using wind magic and a second displacement spell that used spatial magic to propel the user, useful for hunting or any high speed movement - plus totally awesome.
What the eagle men had was different. Their wings generated lift the same way a bird's did — the specific relationship between wing shape and air pressure, the active work of the flight stroke versus the passive efficiency of a glide, the ability to bank and turn and climb and dive through the deliberate use of surface angle. It was physically demanding in the way real flight was demanding because it was real flight, powered by real muscles doing real work.
He imagined how awesome it would be to grow wings and fly that way. He could not give someone eagle man musculature. That would require rewriting the user's physical structure, which was in the category of things he could technically attempt and had filed firmly under: not yet, too much risk.
What he could do was build a construct that materialzed wings and then used mana to release wind and spatial magic from the wings to replac the muscle work. Wings that generated lift not through physical effort but through a continuous controlled mana output, directed by the wearer's intent the way his existing flight spell was directed — with the full range of motion and control that real wings provided.
He wrote for a while.
The core of the problem was the control interface. Physical wings worked because the nervous system was already wired for them — eagle men flew instinctively because their bodies were built for it. A spell-construct wing had no nervous system connection. The user had to tell it what to do, and if telling it what to do required active concentration on seventeen different variables simultaneously, it would be unflyable for anyone who wasn't already doing something equivalent in their daily practice.
He thought about his approach to the companion design. He had built the familiars with deep behavioral intelligence precisely so that the person bonded to them did not have to manage them consciously. The same principle applied here. The wings should not require the user to think about wing mechanics. The wings should think about wing mechanics themselves, and the user should only have to provide intent.
He wrote: the construct reads three inputs from the user. Where do you want to go. How fast do you want to get there. Are you currently trying to stop. Everything else — the angle of the wing surface, the stroke rate, the differential between the two wings for turning, the automatic correction for wind, the transition between active flapping and passive gliding — the construct manages internally based on those three inputs.
He wrote: it should feel like thought. You think left and the wings take you left. You think up and the wings take you up. You think stop and you slow and settle. No more complexity than that.
He sat back and looked at what he had written.
It was, he thought, achievable. It was going to take a few hours of careful construct work. He wanted it for himself — he wanted it quite badly, actually, the specific want of someone who had been thinking about flight since he could think — but the foundation was solid and the control interface was clean.
He powered up all twelve parallel minds and put them to work writing the actual construct.
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He had been writing for about twenty minutes when he became aware that the fairy tale books across the table were no longer being read.
He looked up.
Lyra and Saya were both looking at his notation book with the specific quality of people who had been watching something develop for a while and had arrived at a conclusion.
'Are you building a wing spell,' Lyra said. It was not entirely a question.
Impressed that Lyra was able to decipher his scribbles, 'Yes.'
'For yourself.'
'To start with.'
Lyra looked at Saya. Saya looked at Lyra. Something passed between them that did not require words.
Then they both looked at Arthur.
'Arthur,' Lyra said.
'No.'
'You haven't heard — '
'I know what you're going to ask and no.'
'Arthur.' Lyra folded her hands on the table with the quality of someone settling in for a conversation they intended to win. 'I am your dear elder sister. I have been very patient about many things. I have not complained once about the fact that you have been quietly doing extraordinary things your entire life and the first time you decide to build something purely fun it is exclusively for you.' She paused. 'I would like wings.'
'The mana cost is significant — '
'I have been doing pit sessions for months.'
'The control interface requires — '
'You just said you're making it simple enough for anyone to use. I heard you writing that part out loud.' She looked at him steadily. 'I would like wings.'
He looked at Saya.
Saya was not using words. She was using amber eyes at close range and a tail that had gone to the slow, hopeful sweep she deployed when she wanted something and was trying to be composed about it and was not entirely succeeding.
He looked at his notation book. He looked at the ceiling. He thought about the principles of resisting things you had already decided to do.
'What color,' he said.
Lyra's composure broke completely into something warm and bright and very Lyra.
'White,' she said immediately. 'With silver. Like Tsuki's tails.'
Saya's tail was now wagging at full commitment. 'White and grey,' she said. 'Like — ' She thought about it. 'Like clouds in winter.'
He turned to a new page in the notation book.
'Lyra first,' he said. 'Yours will take longer because of the mana cost adjustment — I need to wire the reserve transfer from your ring into the wing construct's sustain function so it kicks in before you start feeling the strain. You've leveled up enough from the pit sessions to fly for a full hour on your own reserve before you'd feel it, but with the ring backup you could go considerably longer.'
'How considerably.'
'Two hours comfortably. Possibly three if you're gliding more than active-flapping.'
Lyra looked at him with the expression of someone who had asked for something nice and been given something extraordinary.
'Write fast,' she said.
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