"Indeed."

"What happens when they guess wrong?"

"Failure. Of wildly varying kinds."

"Well, that sounds concerning. Do they get spells that do the wrong thing, or nothing, or just spontaneously die...?"

"Any of the above."

"Grand."

"There are vague trends. Spontaneous death is usually reserved for people who were trying to do something very difficult or powerful or destructive. I would be surprised to hear someone died of spell research trying to invent a new scry in a way I wouldn't be if they were trying to invent a potent curse. But there are few guarantees."

"I assume I would wind up inconvenienced in some way if I stumbled across something that would normally kill me."

"A very reasonable assumption."

"I'm amazed there's this much prior art if it's so dangerous."

"What amazes me is that most of the biggest advances in the human magical tradition seem to have been made hundreds of years ago when the human population was comparatively small. Then again, being outnumbered by demons at every turn might be a strong motivating factor in trying to gain power by risky means."

"How much does the human population change in a few hundred years...?"

"Between 1900 and 2000 the human population of Earth went from a little less than two billion to a little more than six."

"Yes."

"Do they have some plan for dealing with that?"

"There are multiple planets in the universe."

"Oh. And they have those fast flying vehicles."

"The problem of successfully conveying humans to other planets and setting up self-sustaining colonies there is not trivial to solve and has not been solved yet, but it can be solved and there's no reason to think they'll completely fail to get around to it."

"That's reassuring."

Shrug.

"I was worried I'd have to eventually think of a safe way for mortals to colonize Fairyland."

"If you do, I'm sure it will help. But it's not strictly necessary to the survival of the species."

"I don't care about the species, just about the individual members of it. If they crowd each other to death that is bad even if some of them live."

"Oh. In that case you might want to make solving mortality your second priority after conquering Fairyland. Priority order suggested on the assumption that the total difficulty of both tasks will increase if you do it the other way around, which I think is plausible. An unconquered Fairyland would make a poor place to put newly ex-mortals, I imagine, and if everyone stopped being able to die the overcrowding issue would get very pressing very quickly in a way I'm not sure space colonization could solve; on the other side of the equation, while it's possible that solving mortality would put you in a better position to conquer Fairyland, it seems likelier to me that it would provide lots of opportunities for obstacles to arise while you're busy. Such as someone from this world figuring out that Fairyland exists and trying to conquer it first, or someone from Fairyland noticing that you're over here amassing power and deciding to do something about you before you become a substantial threat."