The Jagrafess was an ancient, enormous, grey-skinned monster which contains a huge amount of heat, fat, muscle and water, that needed to stay cool in order to remain alive. It was placed in charge of the ersatz Fourth Great and Bountiful Human Empire when it was first formed, in the year 199,909. Outside of its home planet, only a giant facility such as Satellite Five could produce enough cold air to sustain its life. If no cold air was supplied, the Jagrafess would overheat and explode spectacularly.
The Ninth Doctor discovered that the Fourth Great and Bountiful Human Empire was being controlled by the Jagrafess in 200,000, via the news-broadcasting space station Satellite Five, located in Earth orbit. The heat from Level 500 (where the Jagrafess was installed) was channelled away to the rest of the station, allowing the Jagrafess to remain in a cool climate.
Since the Jagrafess could not operate Satellite Five's controls by itself, a human known only as The Editor carried out its orders.
The Jagrafess itself was a pawn of the Daleks, part of a stratagem spanning several hundred years. After its death, the Daleks went on to other stratagems and renamed the Satellite the Game Station.