Dargol was an experimental substance developed by Linea in her attempts to create a "Fountain of Youth". She hoped to eventually use this chemical on herself, but first tested it on two Vyan test subjects.
Not realizing the scope of her project, the Dargol regressed the older individuals into much younger people, wiping them of their memories, something the Vyans would later call the vorlix. Linea herself was exposed to the substance.
Some time later Dr. Janet Fraiser, along with the young Ke'ra (Linea), concocted an antidote for the Dargol to restore the memories of the people of Vyus. (SG1: "Past and Present")