Can anyone recognize a celestial in a vessel? Even with a Perception roll?
No. Celestials have to “tip their hand” by disturbing the Symphony or exercising powers; but then again, Soldiers do that, too, when they disturb the Symphony . . . so, in other words, not by sight or Perception. Some attunements and very good resonance rolls may expose a non-human, but few do so positively under all conditions.
