This one was discovered by in7ac7! Half the hidden tracks are now found. You can get this one at https://soundcloud.com/ditherer/halcyon-prod-blank-banshee or https://pony.fm/tracks/37812-2-of-4-halcyon-prod-blank-banshee

When all of them are found, they'll be added to the official playlist and the Bandcamp release.