The Vulzene were a species. They were involved in an interplanetary conflict with the Malorians.
In a timeline in which Emily Rutherford and Tom Charrington separated as teenagers, the deaths of two Vorlat ambassadors resulted in the wiping out of the entire species, leaving them unavailable to negotiate peace between the Malorians and the Vulzene. When the Third Doctor encouraged Emily and Tom to stay together, the timeline was averted, and the Vorlat negotiated for peace and prevented interplanetary war. (PROSE: Separation Day)