Then you will need to make a different wish and you will not have very long to decide.

"So if I try to make a wish and it doesn't work I'm still stuck making a wish and a contract."

Usually I can tell whether you could succeed at a wish or not. If you want to try the one you just said, you should have a backup wish just in case.

"I'm not sure I want to make a wish if neither my sister or I can get that one. We don't have witches where I'm from and I don't want to be stuck away from home."

"I'd offer to send you home with a full grief seed to hatch, but hatched witches do not grow enough to restock you unless they have people to gobble up, probably a bad tradeoff - and also now that I think of it it's possible that your existing magic will interact badly with you being a soul gem operating your body indirectly."

"If I could make sure they only fed on people like the Golden Diamond General I think it would be a pretty great tradeoff, but I don't think that's workable. And I have no idea how the magics would interact, yeah. So maybe not the best idea, but if there was some way of guaranteeing it would work out..."

"It's not exactly a humane death, I'm not sure how well witches do in captivity in general, and they need several people per grief seed and one seed will only keep you going for a few days of normal amounts of magic use."

"That seems like a really inefficient system. I wonder if it would be possible to make you into one of my kind of magical girl...if they interact destructively then it should just not work."

"How confident are you in that 'should'? Because if it sticks..."

"I mean, even if it turned out that you had to fuel my kind of magic with your soul gem thing too, it's perfectly possible to just not use any magic at all."

"Yeah, but I mean, what if it breaks my soul gem, or it turns out that it does take soul gem magic and it insta-drains me down to witching levels the first time I try anything, or the costumes annihilate each other and transforming means an antimatter explosion the size of the sun, or... You know what I mean? I would like to proceed only with strong theoretical models predicting no disaster."

"I'm having a hard time imagining why it would do any of those things, but it's your decision."

"I basically just need to know a whole lot more about how it works."

"Oh...well, basically if you want power hard enough for a good enough reason, and you have enough 'potential', then you have a subjectively variable objectively instantaneous hallucination where you get evaluated and asked about the consequences of power and whatnot and then at the end it gives you the option to become a magical girl--or boy, sometimes, but that's less common--or not."

"Does whatever system is doing the asking seem to be intelligent?"

"Intelligent..ish? Like, it's computer system intelligent, it can find these people in the first place, but it has no compunctions empowering people who want to do diametrically opposing 'good things' with their powers, like, I know of more than one fundie magical girl who got power on the basis of her faith but also more than one militant atheist."

"Okay. If I can't get power under this system it'll be because it's racist against people from other worlds, but it's not necessarily bright enough to tell me if it'll make me explode. Great."

"Not everyone from our world has the potential. It's possible that people who are not you from your world could do it even if you couldn't. And it's...hmm. It's good at mapping physical consequences? That's a bad way of putting it. When I was having my hallucination I saw...potential things that could happen as a result of having powers, not exactly precog but vaguely similar?"

"That's promising."

"Like, if precog is 'thus and such will happen if you don't act on this vision' or 'these particular actions will have these particular results,' this was more like 'this is a genre of thing you can do if you accept power and make the right subsequent choices'."

"But the thing would probably be precise enough to indicate if I'd wind up dead?"

"Yeah."