It's not quite what you're describing, but in EN Publishing's Monstrous Menagerie II, there's the Eclipsar.
It's got the same naming pattern as planetars and solars, because it's an angel too, but its creation was interrupted. It was left on the liminal cusp of alive and not alive, and it appears as a shadow with no solid form. It cannot interact directly with living things, nor with things that were never alive. It can only touch and be harmed by material that was once alive.
The way it typically interacts with people is to find a corpse or skeleton and puppet it, or perhaps a scarecrow. Many yearn for a divine purpose that their godly creator never gave them, so they'll haunt graveyards or religious ruins, or convince themselves they must slay person X or defend person Y.
If you fight them, their lingering divine essence empowers whatever body they're controlling, so they can assail you, but your own attacks only ever destroy the body, not the eclipsar itself. There is a way to harm one permanently, but I don't want to spoil the mystery if you use one against your players.
