Created by the Ethicals of the Riverworld, Dreamgum is a form of highly addictive chewing gum. It is distributed along with their food to all Riverworlders at each evening meal in their Grails.
It causes vivid hallucinations and a certain degree of lowered inhibitions amongst users. Since the first time it was distributed no one knew what its effects were, the first night on Riverworld was an orgy of sex and violence.
After that, it became a much less popular drug, although a certain number of Riverworlders became hardcore addicts – an addiction that could not be broken by the death and resurrection, as it has no physical component.