The Gravis appeared to confide in the Fifth Doctor, viewing him more favourably than the human colonists on Frontios. The Gravis was more powerful and more intelligent than other Tractators. He was tricked by the Doctor into reassembling the Doctor's TARDIS. However the effort weakened him severely. The Doctor took him away from Frontios in the TARDIS. (TV: Frontios) He later helped the Sixth Doctor to stop Stream's plan to create a gravity machine. (AUDIO: The Hollows of Time)