The House of Zarn was a settlement on the "vampire planet" in E-Space. It was one of the few settlements on the planet that was a considerable distance from the Hydrax. The only contact its inhabitants had with the outside world was Zarn's visits to the castle to meet with the Three Who Rule. During one such meeting, Zarn was infected by them and became a vampire. Upon returning to the settlement, he spread the infection to the entire population.
The Fourth Doctor and Romana II visited and were captured by the vampires. Before they could be drained of their blood, a party led by Ivo stormed the settlement and burnt down the dwellings. Ivo killed Zarn himself by impaling him with a pike. (PROSE: The Eight Doctors)