The Hornets were an alien insect species which resembled the hornets of Earth. They possessed powerful psychic abilities, such as possession of both living beings and inanimate objects and the ability to change both their own size and the sizes of other beings at will. They had a weakness and a disgust for alcohol, viewing beings who consumed alcohol regularly as 'contaminated'. They would wander space in their swarm, invading and taking over worlds until they had exhausted all resources on the planet, at which point they would abandon the wrecked world and move on to the next one.
The Hornets arrived on earth during the dark ages, arriving in Northumberland, near an abbey inhabited by nuns. The Hornets possessed some of the wildlife found in the surrounding area, including a pack of wolves and a pig. However, the pig, which contained the Hornet Queen and a large part of the swarm, was found by the nuns, who believed it to be holy due to the "lights in her eyes", which were in fact the Hornets visible inside the pig. The Hornets were unable to possess any of the nuns due to them brewing and drinking whisky regularly.