Hornet

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. Their powers were much stronger at night, as they found it easier to assert their control over the beings they possessed. They had a weakness and a disgust for alcohol, viewing beings who consumed alcohol regularly as 'contaminated'. The swarm 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 Hornet intrusion on earth began during the dark ages, when the swarm arrived on the planet 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, which meant that they were trapped inside the nuns' abbey. The rest of the swarm, still inhabiting the wolves, attacked the abbey repeatedly, gradually wearing down the nuns' defences.

The Fourth Doctor, on the trail of the Hornets, arrived at the abbey towards the end of the Hornets' assault. After narrowly escaping a wolf attack, he was rescued and taken to the abbey by the nuns, who told him about the pig, who they had at this point appointed their reverend mother. The Doctor realised that the "lights in her eyes" were the hornets, and tried to warn the nuns to no avail about the danger and to plead with them to release the pig to the wolves, however the nuns didn't believe him. The wolves eventually broke down the nuns' defences and were able to enter the abbey through the kitchens, catching them off-guard and severely injuring and even possibly killing many of them in the process. The wolves broke into the inner sanctum of the abbey where the pig was contained, and the Hornet Queen and the other Hornets trapped within the pig were able to leave it and enter the lead wolfhound. The rest of the Hornets from the other wolves also entered the lead wolfhound.

The Doctor realised at this point that the entire swarm was now contained within the wolfhound, and used a bag of aniseed balls he had bought in the village of Blandford in 1832 to lure the wolfhound into the TARDIS with the intention of containing the Hornet swarm and erasing their future actions from history.