I recently came across the Instagram page for Baltimore ritual dark ambient artist, USURPER. After checking out a few posted clips, I immediately checked out the Bandcamp page for a better listen. Fantastic dark ambient audio that could work really well in a haunt setting.
Go check out USURPER's Bandcamp page and download some great tracks and score some super-limited cassettes. Highly recommended, with my personal favorite release being The Disappointment's Room!