I just discovered SheepShaver and I'm mindblowingly excited!
I got all my old Mac games out of storage and began to install all of them.
A trick that I learned awhile ago for making playing games on OS X is to simply make a disk image of the CD and then mount that when I want to play.
I read about a 'technique' for making Riven play without the Disks which is essentially to edit the riven.cfg file that comes with the install to no longer point to the CDs but instead to point to local directories. I figured something like this should be possible with Myst.
Turns the Myst app looks to be some sort of Hypercard script. I made what I felt was a logical edit to it which was removing all
Myst: prefixes that I could find in the file but that makes the app inoperable. I figured someone else would know how to do this better than me.