Sounds like a good plan! If you make sure to keep changing/advancing the feeling of dread it should work great. Don’t keep it a constant, make it come closer or disappear or let them discover new things about it on a smaller scale. Most times you bring it up there should be some small progress toward figuring out who/what it is.
I use something similar though more specific since they already know who the villain is, he’s just not on screen.
Without darkness, there is no light. If there was no nighttime, would the stars be as bright?