"Mountains that lean over" ....
See, every once in a while the Sun gets drunk and flies too low. The pointiest peaks tend to start to melt - thankfully when he splashes down in the western ocean, it sobers him up fast, so the SizzleDays only happen one at a time. And the hangover is truly cosmic, so the memory of the aftereffects keeps Sun flying right for long periods between. Terribly hard on the living - only cavedwellers and fish survive, and half the fish wind up broiled. Since the underfolk appreciate over-surface things like pork, and chestnuts, and cotton underdrawers, they keep a stockpile of seeds and livestock below, just against that next sky-revel-tipsy day.
They also tend to travel aboveground at night, just in case....
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Not saying you even need to rationalize, Abu Lafia, but Chick knows I can't resist what-if's and but-maybe's :-). Leaning peaks could even be just a style thing for your in-character cartographer - mountains so steep they certainly SEEM to loom right over a traveller. She's right - that kind of detail takes a view right out of 'realism' and plants it in 'fantasy' for me too - I'm just willing to suspend disbelief for the sake of a good story. And your 'story' writ in map form is already nice - can't wait to see it develop further.
Oh, and thanks for showing us & expanding on JEdwards' tutorial!