Rogue Legacy Wiki

The dementia trait will cause players to sometimes hallucinate monsters which don't exist.  These monsters behave as normal, but do no damage, cannot interact with the player in any way, and will have question marks floating above their heads when attacked.  The hallucinations may be monsters from any area of the map, not just the one the player is currently in, which provides a useful clue to whether a monster is hallucinatory.