Gravis

Gravis was leader of the Tractators that inhabited the planet Frontios. He appeared to confide in the Doctor, viewing him more favourably than the human colonists on Frontios. Gravis was more powerful and more intelligent than other Tractators, after being tricked into doing so by the Doctor he was able to reassemble the Doctor's TARDIS, however the effort severly weakened him. The Doctor took him away from Frontios leaving him on an uninhabited rocky planet called Kolkokron. (DW: Frontios)