Krafayis

The Krafayis were a species of space-faring predators.

Biology
The Krafayis are a race of bird like creatures who originate from all over the universe. Their life is similar to one of a birds or vultures. They are raised and then voyage forever attacking and defending its fellow race. It is invisible to the naked eye but could be seen by Vincent Van Gogh, it is unknown why he can see them. The Doctor also used a device that he was given that can see invisible creatures, He used this to find out what they were and have a good look at them. (DW: Vincent and the Doctor)

Life cycle
During their early life they are nurtured in a similar way as a bird would be. After about the age of several hundred they go on a never ending voyage with up to three thousand other Krafayis journeying across the universe and devouring creatures they find. (DW: Vincent and the Doctor)

History
The Krafayis have travelled the universe since the late Dark Times and have a unique defence system where they cannot be seen by the naked eye. They have voyaged across the universe in packs and devouring many life forms. One was left behind on Earth and was scavanging on humans. It was confronted by Vincent Van Gogh and later killed. (DW: Vincent and the Doctor)