Krafayis
The Krafayis was first seen in the Eleventh Doctor episode, Vincent and the Doctor (Series 5 : Episode 10), causing destruction and chaos in 19th Century France. Krafayis are large creatures, featuring parrot-like beaks, large necks, two wattles (on the side of their head), a quill like horn and quills on their tails. Generally Krafayis are invisible, offering them the greatest protection, though Vincent can see them due to his unique perception on the world. They can also be seen in reflections, such as mirrors or water. The Doctor reveals that the Krafayis hunt in packs, and when they leave a planet they also leave behind weaker members of the hunting pack. In the episode in which we see a Krafayis, it is blind which is why it was left behind on Earth. Krafayis that are left behind become lonely and cause chaos until they are killed. The Doctor attempts to confront the Krafayis, but is unable to see it as has to be rescued by Vincent warning him of its position until the Doctor decides that it is best to hide. The Krafayis attacks Vincent, who defends himself and accidently kills it.