The Spectral Mass, also known as The Collective, is a gigantic supernatural monstrousity that is a mass of ghosts reformed after Robo-Buster dispersed them, and it is the main antagonist of the episode "Robo-Buster" of The Real Ghostbusters cartoon series.
A company called Grossjuck Industries has created a machine called the Robo-Buster, which was tasked with eliminating paranormal threats everywhere in New York. Its proton technology claimed to destroy incorporeal entities, though it turns out that it shifted the entities into the space-time continuum. As a result of the entites building up into the continuum, an enormous kinetic energy buildup led to flux in the etheric continuum, resulting a formation of one humongous ghost manifested from the essence of all of these "destroyed" ghosts.
Robo-Buster "destroyed" the giant mass after its initial manifestation above a park, but it later appeared at Grossjuck Plaza. As it turns out, the mass wanted revenge on Paul Smart, the president of Grossjuck Industries who unleashed the Robo-Buster on them. It tried to zap at the person, but it kept on reforming after parts of it were destroyed. One of the ghosts then possessed Robo-Buster, but was exorcised by the Ghostbusters, who defeated the Giant Mass Ghost by laying out ten traps and catching all of the ghosts that made up the huge phantom. Robo-Buster also helped after Egon adjusted his proton cannon arms to work like regular proton guns.