Krafayis

The Krafayis were a species of space-faring omnivorous predators.

Biology
The Krafaysis were large creatures, with both reptilian and bird-like traits. They had parrot-like beaks, a quill-like horn, two wattles on the side of their heads, long necks and quills down their tail.

The Krafaysis were generally invisible, allowing them the perfect defense. They could be seen by Vincent van Gogh (apparently due to his unique perception of the world) and in the reflection in a mirror on the Visual Recognition System. (DW: Vincent and the Doctor)


 * Whether they could also be seen in other mirrors is unknown.



Life cycle
The Krafayis were somehow capable of travelling through space, moving from planet to planet to hunt. They preferred to travel to planet with oxygen/nitrogen atmospheres, such as Earth. They hunted in large packs with a strict hierarchy and had territories which spanned star systems. Eventually, they would leave the planet, leaving behind the weaker Krafayis. These Krafayis would be unable to rejoin the pack and in their loneliness would cause destruction and chaos until they were killed. (DW: Vincent and the Doctor)

History
At some point before 1890, a pack of Krafayis came to Earth, fed and left. One blind Krafaysis was left behind in France, where it attacked several people. It was also seen by Vincent van Gogh and painted into The Church at Auvers.

When the painting was seen by The Doctor and Amy Pond, they travelled back to before it was painted to investigate. During the visit, they saw the remains of one of its victims and were later attacked by the Krafaysis. The Doctor was eventually able to identify it and planned to confront it in the church, stunning it with his Sonic Screwdriver. This attempt failed, and the Doctor, Amy and Vincent were forced to hide. The Krafaysis followed them and attacked, forcing Vincent to fight back and accidentally kill it. Following this, the timeline was changed and the Krafaysis never painted into The Church at Auvers. (DW: Vincent and the Doctor)

The Doctor may have previously encountered the Krafaysis in the jungles of the unnamed planet where he first met Leela. When the Doctor realized that there were dangerous, snarling creatures close by, Leela says "They can't be seen; they are phantoms." The Doctor then says "To our friends, whatever they are, the visible spectrum is irrelevant; they're blind." The Doctor goes on to say that these creatures are attracted to sound and vibration. (DW: "The Face of Evil")