What do you think about the introduction of 'modern' humans, or Earth-like people and devices, in the middle of a fantasy book that is set in a completely invented world?
I fear I'm getting ready to read about such a reveal (many hints so far have driven me there), and I'm not that comfortable or happy about it...
I think it can be done properly, but sometimes it feels like a 'lazy way out', something that's just there, ready to explain a bunch of things.
A bit like that scene in Indiana Jones when he's being attacked by a guy with a big knife, who starts doing al these fancy moves, and suddenly Indy takes out his gun and just shoots him. Yes, it's funny and a way to easily get out of that situation, but it feels wrong for me in books, after being invested for so long (because I'm complaining more about the big reveals rather than when it's kinda obvious from the start).