Uncanny X-Men (1963 1st Series) #404

The true villain behind the X-Corps/Human Resistance conflict is revealed ? but it may be too late for Banshee, or the X-Men, to do anything about it! And as an army of Multiple Men storms Zurich, Chamber (soon to star in his own X-Men Icons series) takes a guided tour through Mastermind's subconscious... where he's forced to confront some not very pleasant truths about himself! ?