I see DVW discusses PLATO's multi-user games in the section "The Fifth Age", at least Orthanc and Oubliette pre-MUD1 (Essex MUD; 1978), saying "the interaction

I see DVW discusses PLATO's multi-user games in the section "The Fifth Age", at least Orthanc and Oubliette pre-MUD1 (Essex MUD; 1978), saying "the interaction it allowed between characters was very limited; it was almost there, but not quite". Were there other world games on PLATO in the 1970s? (Same section adds "In late 1979, the first ever fully-functional graphical virtual world was released [on PLATO]: Avatar.")