I think the track is “Train Heist”, I believe it is the music from the campfire conversation the night before the heist.
Since the Dyad is mentioned maybe it could tie into that. I think it would be interesting if the Dyad was somehow related to Mortis. Like the Dyad, Ben and Rey, have taken the place of the Son and Daughter.
EDIT: Also, I’ll make an updated version taking all of your comments into account!