The Tharils were a race of leonine time-sensitives who could time-shift, and therefore travel through the time vortex unaided and unharmed by the time winds encountered by the Fourth Doctor.
The Tharils were gifted with time sensitivity powerful enough to navigate a ship. Due to this sensitivity, only dwarf star alloy could contain them. The Tharils could ride the time winds. In appearance they were almost completely covered in hair, and all the males had long beards. They had slightly cat-like noses.
The Tharils once controlled a vast empire centred on the gateway, a huge castle that stood at the border between N-Space and E-Space. The Tharils could pass between the two universes via gateways in the castle. Anyone else who passed through met a dead end.
The Tharils enslaved many species, including humans. The humans built robots called Gundans as they were unable to approach the gateway. These robots attacked the Tharils and invaded the castle during a banquet for the Tharils' kings.
As the Tharil Empire crumbled, the humanity began to exploit their former masters in a continuing cycle of oppression. The Tharils became the slaves, forced to serve as navigators of the time winds and traded as rare and valuable commodities. Ships likes the privateer under Rorvik, which was moored in the Gateway, were built of dwarf star alloy to prevent the Tharils escaping. When Rorvik's privateer became stuck in the Gateway, the Doctor and Romana befriended two Tharils, Biroc and Lazlo. They explained the history of the Tharil race. The two Time Lords helped to free Tharils still trapped in the privateer.
Romana stayed behind in the Gateway to help the Tharils build a new life, based on freedom and equity. (TV: Warriors' Gate) She spent many years living amongst the Tharils, travelling E-Space, freeing them from slavery. (AUDIO: The Invasion of E-Space) When she became President of Gallifrey, Romana entered into negotiations with the Tharils. (PROSE: Lungbarrow)