An enemy cast sabotage on a creature of mine, and it attacked a laughing wisp. Ethereal activated and was logged in the history, but then the text “Laughing Wisp took 0 damage. -5555” appeared. I didn’t notice anything happen to the wisp after that. I did catch a screencap of the log:
I’m running a necromancer/minion-based build, dire wolves were active and I’m fairly low level here, in the 40s, if any of that matters.