Usurian

The Usurians are manipulative life forms native to the planet Usurius. They don't need to breath and look like a small handful of green kelp in their natural form, although they belong to the fungus, not vegetable kingdom., As long as they expose themselves constantly to particle radiation they can assume the shape of a dwarfish humanoid. They are listed in Professor Thripsted's Flora and Fauna of the Universe as poisonous fungi.

Though they were originally a war-like race, this was inefficient and so they turned to commerce, creating the Company. Apparently very knowledgable, their databases contained information on Gallifrey (which they did not consider a viable market for their consumer products) and knew of the the Doctor's previous acts "economic subversion".

The Company moved the Humans of Earth to Mars after Earth became inhabitable because of pollution. The Humans were nearly taxed to death. When Mars also became uninhabitable, they moved the humans to the city of Megropolis One on Pluto and set up six artificial suns, They drugged the humans with sedatives, exploited them and ruthlessly taxed them. (DW: The Sun Makers)