Master Cosmos was a Class 7 sorceror who lived in a place called Greenstown. The people of Greenstown knew too much and wanted Master Cosmos to seal the town from the rest of the world. Cosmos did so and also gave them immortality, but the price the people paid was that they had to live in their bodies as they continued rotting and decaying. His daughter Denetia Cosmos escaped Greenstown and got the Ghostbusters to help her defeat her father and free the souls he imprisoned. After his defeat, the people's souls were able to roam freely and Greenstown came back to existence.