A little background: I am designing a campaign that largely takes place in the mind of a twisted wizard. The wizard was shunned and exiled from his home due to a physical disfigurement, and after a hundred years of solitude, he has gone mad. His latest infatuation is the PCs. Throughout the adventure, he will be imparting communal dreams upon the party in which they must deal with some element of the wizard's past -- like Hatred, Guilt, Rage, etc. These dreams are (in D&D terms) encounters in which I try to inflict these sort of emotions upon the players.
I'm a bit stuck on Loneliness and Betrayal. I've toyed with the idea of making certain PCs invisible, silent, and incorporeal, but that singles out one person in the real world and would not be engaging gameplay. I've thought about giving each party member a separate dream in which the rest of the party turns on them, but that would require running six concurrent encounters which does not seem very possible.
In what ways can I convey a sense of loneliness and betrayal to the party as a whole, without singling anyone out or having it be an impossible or boring encounter?
Side note: My players are gung-ho about combat encounters, so it is preferable if this sort of thing could be pulled off in the heat of battle rather than just RPing it.