This species is never referred to as “Herazi” in the story. The Doctor says “Heziri” or “Heyziri” depending on how one would spell it.
Talk about it here.
The Herazi were a species who ran an intergalactic reality show, where the main race would invade a different planet every episode. They had been involved the show since its first season.
When ratings would begin to fall, they would bring in a new species, getting them to kill off the past species that ran it. They would not tell the new species that the species they'd killed off had been part of the show.
In 2007, they "invaded" Norwich alongside the "Zaross", as part of the filming of a new episode for the show. Jackie Tyler was there at the time and so, called Rose Tyler and the Tenth Doctor to help. (AUDIO: Infamy of the Zaross)