In SSaDT on the introduction page to the 4th edition storyline there is a single panel where Redcloak is telling Xykon to turn off his necromantic aura(Which Xykon seems unaware of)

The MitD exclaims "I don't even know if I'm affected by that, Have I even been updated?"

Could this be a clue pointing at a monster who was excluded from 4th edition? OR at a monster who WAS updated to 4th edition, excluding those who weren't?

Not sure if this has been brought up before.