The Gabrielideans were a liquid-based lifeform.
Before being converted into an idea-based lifeform by the Enemy, the Shift was a Gabrielidean soldier fighting for the Time Lords against the Enemy. (PROSE: Alien Bodies)
Behind the scenes
The Gabrielideans may be associated with Droge of Gabrielides, whom the Fourth Doctor said had offered an entire solar system for his capture. (TV: The Sun Makers)