"They have a lot of magic, and sometimes someone convinces one to do them a favour, but they really don't like killing people. So somebody won a favour from an athra and tried to come up with the most inevitably fatal curse they possibly could that didn't directly mention death, hoping the athra wouldn't figure out that cursing me to shatter into little pieces whenever something hits me hard enough was effectively murder, and the athra cursed me exactly as specified but then also made me immortal."

"That's, uh, weird. Convenient in a horrible sort of way?"

"Athrai are weird! Their minds really don't work like human minds. They can take any form they choose, and some of them try to pretend to be human sometimes, and I can always tell."

"Okay. Next question is where are we?"

"Weird barren wasteland with weird magic. I've been trapped here alone for months with no idea how I got here or how to get home and I'm pretty sure I'm the only person on the planet and I'm kinda going insane a little."

"Oh. Well, I'm not a hallucination, if my saying that helps, which it probably shouldn't. No idea at all?"

"I went to sleep at home and woke up here."

"Well that sounds distressing. Are you just sufficiently immortal to handle being in a barren wasteland?"

"The weird magic makes it less barren. I, uh, can't starve or die of thirst, but I do actually have food and water; I hauled the big plate way out here because I wanted to test that diagram without risking blowing up the hill I'm living under. And look how right I was!"

"So right!" Cam agrees. "I didn't get a good look at any of it before it exploded."

"As far as I can tell, that diagram was supposed to build a house."

"If it weren't for the part where it's probably not supposed to explode, you could declare it an indirect success?"

"Are you offering to build me a house?"

"Make you a house," Cam says. "Demon, remember, we're useful."

"Well, I won't say no," he says.

"What sort of house do you want?"

"...You know, I'm really not sure. But I probably want it closer to my hill. Unless you can make me a mountain range, in which case I want it farther from my hill."

"I can make you a mountain range! Why the preference for unlevel terrain?"

"The hill is where I found all the supplies I'm using to do local magic and books I'm learning local magic out of, I'm not attached to its hilliness in particular. The mountain range is because I grew up in one."

"I can probably just copy the one you are from, if that would not be weird for you."

"Wait, really? And no that would be really weird and not in a good way."

"I have pretty good copying-stuff powers," Cam says. "I can also just give you, like, the Catskills or something, or design a mountain range which has not previously mountain ranged somewhere else."

"If I have all these options I think custom mountain range is my favourite, but I've never heard of the Catskills so in fairness I wouldn't really be able to tell the difference," he says.

"Do you want to design one yourself? I can go off blueprints. Or, like, a topology map."

"I've never designed a mountain range before, I have no idea of the operative engineering considerations! ...But yes I totally do!"