Oh, no need to go as far as to say that you're exposing yourself, this merely means that I've wasted way too much of my time on Fate-related content~

But yeah, the poison I was referring to was actually mentioned in a short-story aptly named Zugzwang, included in the 10th Volume of Type-Moon Ace, which details the exploits of en elite unit called Zugzwang in the /Apocrypha Universe. After looking for the quote I actually realized that the poison only hindered the production of its victim's Magic Circuits, not completely numb them, so I made a blunder by misremembering that fact >.<
They appeared in the /Strange Fake novels too, but the quote in question comes from the /Apocrypha short-story in which they are slaughtered by Assassin of Black shortly after she was summoned by Rikudou Reika. It's more or less a prequel to the events of the main series, though solely relevant to the Rikudou Reika and Assassin of Black.

[quote]A man with a black-coated dagger and blowpipe in his hands spoke. The dagger and the darts of the blowpipe had paralysis poison coated on them. This poison, made for use against magi, did affected not only the body, but also someone’s Magic Circuits, and though it didn’t completely stop them, it did remarkably slow down their ability to weave spells.[/quote]

In any case, it's interesting to hear where you drew inspiration from in regards to your ability, and I think it's fine the way it is since it isn't really game-breaking and doesn't conflict with anything in-universe as far as I'm aware, but my memory is spotty so take that with a grain of salt T.T
So yeah, like I said, I'm actually a fan of the concept behind those abilities of yours, so my mind went a bit wild to neatly fit them into the Fate Universe, which is why I prattled on an on about the mechanics and functionality, but that was just on my own personal whim. I like discussions like these, so I could quite help myself, my bad xP

But well, in the end it's up to the Mods to decide.