Weird capitalization, much?
Natural disasters had become more frequent in the area since the remains of the high priestess vanished from her tomb. The locals believe her final resting place was built over a gateway to the underworld, and she was their protector.
It would be okay (not standard, but okay) to capitalize High Priestess if the author wants to go for that Old-Style High Fantasy Effect, but it makes no sense to capitalize only part of it; either capitalize both high and priestess, or capitalize neither. It makes no sense to capitalize locals, either.
It is neither necessary nor desirable to use had in front of every single verb that’s before the “now” of the narration.
Ellipses at the end of a sentence (or partial sentence) indicate a trailing off of the thought. Don’t use them just to indicate that you’re done talking for now; that’s what a period (a full stop, to those who speak UK English) is for.