When spoken to, Wunalz will ask the Vestige if they hear the call of Sithis. When told no, he will deduce that the Vestige must be living. By saying this, Wunalz is one of the only ghosts in the Temple who is aware that Vestige is not dead, but he is.
"Do you hear the call of Sithis? It was drowned out by the wailing spirits, but now they're at rest."
- I don't hear anything "Then you must be of the living. My eyes are veiled. My time here draws to a close."