The inspiration:
In
Fate/Stay Night, Rin gave Shiro a jewel fom her collection to act as a switch that kept his magic circuit "always on" and allow him to better use magic, instead of having to recreate a new circuit every time he wanted to use magic.
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I reinterpretted that, and in
Nanoha/Cente Gravia:
Sophia wanted to help Kha store his mana better, as his Reactive Linker was bleeding mana all over the shop, therefore causing his magic stamina to be much lower than it's supposed to be. After reading up, she found that treatment was to core the Linker Core with a special jewel, and Sophia had a stock of those gathered by her family over the years. She dug out the most powerful one and gave it to Kha to swallow.
Expected side effects aside, and Kha becoming able to Trace a few more times without suffering a heart attack, this was also the first step of Kha learning the incomplete Reality Marble,
Infinite Spell Forge. It is from this platform that Kha springboards and learns more about his Rare Skill
Tracing, and ultimately attaining
Unlimited Blade Works in StrikerS.
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Then came the revelation of what Relic infusion meant in that episode of Vivio's memorable screaming (almost gave me tinitis. >_<). Now considering that Sophia's father worked with Jail in the Sacking of Renault, I'm not surprised that among those red gems was a Relic. And the way the Relic awoken Vivio's barrier IS is exactly the same as Kha finding
"Infinite Spell Forge".
It made me fall flat on my face, as I realized that that innocent little red gem that Sophia gave Kha... worked exactly a Relic, and it might as well be one.
And there's one more coinciding factor: it was coincidence that Kha was named after a letter in the alphabet (see 3rd edition Codex for details), but the largest coincidence by far was that his name was the
11th letter of the alphabet...
...now ponder about Relic #11, then add Khrack of Jail being obsessed with Kha for a reason unrelated to Relics...