The Hoolox were an ape-like warrior race. They were one of the races along with the Nin, and the similarly warlike corocdile-like Sraal, were duped into beleiving that they have rightfully bought the Earth. However, that was a mistake due to the human boy, Robbie, who was then playing with it, not knowing or intending what would happen.
Not convinced with the doctor's explaination, the Hoolox launched a missile attack that was powerful enough to burn the planet. (COMIC: The Day the Earth Was Sold)
The Doctor was able to enlist the help of the formally duped but peaceful Nin to prevent the attack. (COMIC: The King of Earth)