Rempath

Rempaths are parasites usually from the Rafirax system. They are transmitted through the internet and infect hosts via the technology they use. They are then carried in the blood where they feed off emotional energy and multiply.

They induce an anger in their hosts which grows and grows eventually resulting in violent rages followed by a fatal heart attack.

Gully was using Earth as a Rempath farm in order to take revenge on The Doctor and to sell as weapons.