What happens if a Demon tries the Mind Reading form ability on an angel? The rules from the DtD manual state:
System: The demon only has to see her intended target; the target does not have to see the demon or know she is there. As a reflexive action, the player rolls her Wits + Persuasion + Primum vs. Resolve + Primum. If successful, the demon can read the surface thoughts of the victim for as long as she maintains concentration.
It's odd that the manual assumes that the Demon is trying to read the mind of another Demon (hence the "vs. Resolve + Primum"). Angel's don't have Resolve, so maybe Resistance+Rank?
If it's successful, does the Demon know that the target is an Angel? Does the Angel have any way to detect the use of an ability on them? Otherwise, this seems like a perfect Angel-detector.