Quick Q: Can a wraith see a priest using etherealness?
Thanks!
Depends on your interpretation.
An ethereal creature treats other ethereal creatures and ethereal objects as if they were material.This suggest they can see each other. But...
An ethereal creature is invisible
So maybe they can't see each other, unless they can see invisible (material) creatures.
It can't, unless that particular specimen formed or was transported to Ethereal Plane. You are confusing state of incorporeality, which is lack of physical body (having only spiritual form) with being ethereal, i.e. existing on/being phased to the ethereal plane.
Ghosts are beings that are ethereal but can manifest as incorporeal being on material plane but that's separate case.
Wraiths are not ethereal so it doesn't matter how ethereal creatures treat other ethereal creatures since only the priest is ethereal. Because he is ethereal, he is invisible. Wraiths have no natural ability to see invisible so the wraith cannot see the ethereal priest.
However, the wraith has Lifesense and the priest is (presumably) alive, so the wraith can probably still sense him. there is nothing in the Etheral state that says he cannot be sensed, and nothing in the Lifesense ability that precludes sensing creatures on overlapping planes.
On the other hand, the priest is literally on the Ethereal plane, so he might not be "within 60 feet" of the wraith if we rule that being on another plane means he is not on the Material plane AT ALL. Since the two planes "overlap" I tend to assume that the ethereal priest is still, remotely, on the material plane and therefore, when he is within 60 feet of the wraith there is enough life there for the wraith to sense. I could easily see other GMs ruling that differently and I have no idea if there is any official word on such things.
These were very helpful answers. Thank very much!